Lots of people are talking about cutting Cultbrand Cinder for Rakdos Shred-Freak for the B/R hybrid slot. This is probably a good time to have a discussion about Cultbrand Cinder. At first I added it because it was the best B/R hybrid I could find, and thought it would be a decent filler card. After playing with it enough though I have come to appreciate it's value. Often times it'll flat out kill a creature. There are a ton of very good creatures in pauper cube with one toughness. Even if you can't out-right kill a creature, putting a -1/-1 counter on a creature will probably be able to marginalize it. Being left with a 3/3 is pretty nice, as 3/3s in pauper cube tend to beat pretty hard. Especially in red and black where you don't get much bigger.
Shred-Freak on the other hand is just a dime-a-dozen two drop. If it were either mono-red or mono-black, it might not even make it into some people's cubes. Is it really much better than another 2/1 for 2?
Azorius Arrester - This fits well with white's theme (in my cube at least) of fast aggression. On turn 2 it's on curve. On later turns it helps you punch through damage. White has a ton of better 2 drops, so I wouldn't be shocked if someone doesn't want this. Cubed
Concordia Pegasus - I actually really like this card, but it doesn't fit at all with white in my cube. If white is slower/flying based in your cubes, consider it. It's very efficient. Depends
Keening Apparition - Shoutout to very large cubes, here's a third Kami of Ancient Law. It's a spirit, which is a more relevant creature type than Unicorn, so you may want to replace the ronom guy with this as your second. Size matters
Sunspire Griffin - If you're still running Cloud Crusader you should probably have replaced them with these guys by now. I think that these guys are great and am happy to have another. Cubed
Swift Justice - In the world of tricks, this one is pretty good. I like other tricks that go better with aggressive decks more though. Probably not
Stealer of Secrets - These cards are very good in control/removal decks. I'll probably fit another in, althought I think having a 1/3 is better than a 2/2 in this situation. Depends
Voidweilder - I love me an Aethersnipe, and having a 1/4 tacked on is very nice. There's a limit to how many expensive blue creatures you can fit, and this is only the 4th best version of this card. Depends (but I will add it)
Dead Reveler - Black is pretty weak at 3 drops. I think that this is better than a 3/2 vanilla, so it'll make it into my cube. Probably
Grim Roustabout - I like the flexibility of this card. Some black decks want the blocker, some want the bear who is hard to block. This guy looks very nice, just make sure you can commit to the aggression once you put the counter on it. Probably
Perilous Shade - This card is amazing. The best card for us in the set.
1) It can block right away after playing it on turn 4.
2) It is not vulnerable to removal when your mana is down. 3) You can play it in two color decks because of the half colorless activation cost.
Shades are very good cards, but are limited by being very black-intensive. This one being great in a two color deck really puts it over the top, as well as the great body size. Late game this is unstoppable, and when you drop it it'll help get you to late game. Staple
Terrus Wurm - Worth noting for being very fat. If you want a late game option, this one is a great add. Depends
Gore-House Chainwalker - 3 power 2 drops are nice. I'm not as in love with it as everyone else, but it definitely beats out stuff like Ashmouth Hound. Cubed
Splatter Thus - A 2/2 first striker for 3 is pretty good on defense when you need it. 3/3 first strikers are hard to block. I don't see how you leave this out. Cubed
Tenement Crasher - I actually run Flameborn Hellion in my cube, and am pretty happy with it. Nothing I'd rather see in top-deck mode, and it's pretty easy to catch people off-guard with it. This is a strict upgrade, but I don't think everyone wants red six drops. Depends
Drudge Beetle - Grizzly Bear is very far from playable in green, and the Scavenge cost is huge for just two counters. I'm probably leaving this on the sideline. Probably not
Korozda Monitor - Four mana 3/3 is pretty mediocre in green, but three counters is fairly significant later. Expensive to scavenge, but turning your mana dork into a 4/4 is very nice. There are too many good green 4 drops, though. Probably not
Centaur Healer - This is a very nice mid-range card, and should be on the list when considering g/w gold cards. Depends
Goblin Electomancer - This looks like a solid card for red/blue. It's got some very stiff competition, but I think it'd be really fun to have around. Depends
Hussar Patrol - Great card in a weak gold color combo. Cubed
Sluiceway Scorpion - This a very good. g/b has some strong cards, but I think this actually competes with them. It's like having Consume Strength as a creature. Staple
Spawn of Rix Maadi - With the amount of removal in these colors, a 6/4 for 5 that can't block sounds like a good deal. Depends
Frostburn Weird - Great blue card, mediocre red card. Still, I'll probably use this over Noggle Bandit as my u/r hybrid choice. Probably
Safehold Elite - not that good of a card, but it's all we have. Some decks just want a bear, so I do play this pretty often. Minister of Impediments - free trapper is pretty nice. Plus, blue doesn't get much of this, and really likes it. Scarscale Ritual - This card is alright. There's not much else to choose from. I do wish there was a better option. I used to run Lurking Informant, but it's just too slow. Cultbrand Cinder - this card is WAY better than you'd think. I run it in just about any black or red deck. I would run it even if I didn't have a dedicated hybrid section. Giantbaiting - This card is mediocre, but it has a place in super aggressive decks. Not much to choose from here, but this is good in aggressive decks that have a good curve. Snakeform - favorite card ever. This thing is sweet. Noggle Bandit - this guy is decent. 2 power evasion for 3 is par in blue, but it's great in red. Fire at Will - This is actually usable in decks that aren't R/W. It has a ton of upside, and almost always kills something. This card is pretty good. Unmake - pretty much on par with fire at will. More consistent and good vs green, but can't 2-for-1. Desecrator Hag - Green loves this card, and black is always willing to run card advantage. Good stuff.
I'm going to write up a review (for the whole set, separately, too) and don't want to read anyone else's opinions yet. Afterwards we can compare notes. I usually am interested in some cards that pass by, so we'll see how it goes.
Here's my quick and dirty pauper cube review. Cards that are not noteworthy are not noted. Bolded cards are ones that I will try out.
Avacynian Priest - 3x blinding mage variants makes this guy pretty sad. Chapel Geist - Nice body on this flier. I think this is better than the first striker, even with the double white.
Feeling of Dread - I love these types of cards, but needing to be U/W really kills it.
Moment of Heroism - I think this is better than Mighty Leap. I would rather play the universal Fortify type pumps though. Rebuke - AWOL, but more main-stream. This is probably better than a few white removals I have. Spare from Evil - there are a lot of variables at work here. I don't think I can fit any more utility spells though.
Village Bell-Ringer - 3 drops are really tight, but this is a sweet trick. Doesn't really fit with white, unfortunately. Voiceless Spirit - Nice flier, but again, 3 drops are packed. I think this is better than Cloud Crusader, though.
Claustrophobia - Good blue removal. Delver of Secrets - Exactly what you want. Small mana investment, big payoff.
Forbidden Alchemy - my views on Impulse have been well known. It isn't very good, since the card quality in pauper cube is pretty steady. I would rather have card advantage than card selection. Makeshift Mauler - The drawback is non-existent, and a 4/5 for 4 is pretty big.
Moon Heron - 3 power fliers for 4 have long been out-dated imo. Sensory Deprivation - Nullify a creature for 1 mana? This might actually be decent. I have to think about it more.
Silent Departure - bounce is way too good in pauper cube to consider this. Stitched Drake - already mentioned. This is exactly what blue wants.
Stitcher's Apprentice - too hard (impossible?) to abuse.
Dead Weight - pretty cheap. I think I'd rather have an instant, but this kills a lot, so maybe it's worth it?
Ghoulraiser - I wish this could be added. It's going to be awesome in limited. Markov Patrician - I love child of night, this is even better. Stromkirk Patrol - this is probably the fattest black creature behind Abomination available. I'll debate it over Zombie Boa. Vampire Interloper - sweeeeet. Victim of Night - top tier removal spell.
Ashmouth Hound - too many good 2 drops. I don't think this is too close to making the cut. Bloodcrazed Neonate - great when backed by removal. Brimstone Volley - deals a lot of damage, and I don't think morbid is hard to trigger.
Kessig Wolf - it's a bit pricy to activate, but War-Spike Changeling is pretty great.
Night Revelers - this probably has haste a good amount of the time. I don't really run 5 drops in red though. Nightbird's Clutches - this is a solid faulter effect. Pitchburn Devils - seems like a great high-end card for an aggro deck. Village Ironsmiths - 3 power 2 drop, kind of...
Ambush Viper - Awesome card. I think this actually makes it into normal cubes, too.
Darkthicket Wolf - too many good 2 drops, even if this is hard to block. Festerhide Boar - Morbid seems easy to trigger, and a 5/5 trample for 4 is a sick deal.
Orchard Spirit - this is a reprint of Treetop Rangers. Prey Upon - seems like solid removal. Ranger's Guile - seems great vs removal. not sure if that's enough, though.
Spider Grasp - expensive, but great on defense. Woodland Sleuth - green would love a gravedigger. Being random is kind of a shame though.
Drake, neonate, and interloper are certainties IMO. Don't think of drake as a 3 drop and it'll be a lot better. Play it late, and you can easily keep counter mana up. It's quite good for a control deck.
Neonate is amazing in an aggressive deck. Back him up with a little burn and you will end the game quickly.
I don't think Stitcher's Apprentice is very good for cube. It's an interesting effect, but it's only good if the sacrifice part gives you some kind of advantage. Cube has little "dies" or graveyard triggering stuff, so I don't see it being very good. At it's best it hoses pacifisms. At it's worst, you can upgrade your 1/1s into 2/2s. Hooray.
Village Ironsmith and Spidery Grasp both intrigue me. 3/1 first strikers for 2 are no joke, but 1/1 first strikers for 2 are pretty bad. Unlike Neonate, you can't use removal to make him insane, you just have to hope your opponent is control and lacks in 2/3 drops. Late game he's pretty safely a 3/1 first striker, though, and 3 power first strikers are somewhat hard to beat in pauper cube.
Spidery Grasp is a great trick, and fits what green is doing pretty well (midrange aggression). It lets you get the beats on while making sure you don't lose the race if your opponent started aggressive. Also, it's a good out to stuff like Errant Ephemeron. It's obviously not better than the premium pump (wildsize and vines), but it's probably better than a lot of other stuff.