Suggestions:
Ophiomancer: good snake-maker. Synergistic with Ertai. Good "rattle snake" card...
Phyrexian Arena: I have a hard time not putting this in every deck containing black ever.
Dictate of Erebos: Strictly better than Grave Pact in a 3 color deck. Only item of concern is curving into your commander, but this is one you'd likely use after you cast him anyways.
Seal of Cleansing: synergy with Ertai, good rattlesnake, I'd run this over Disenchant.
Seal of Removal: You may or may not want to run this, but again it is a good rattlesnake card (people hesitate to attack you), good utility, synergy with Ertai.
No Mercy: people sometimes don't like losing attackers.
Silent Arbiter: Great Pillowfort card.
Mystic Remora: auto-include in blue, synergy with Ertai.
Cuts: This is the worst part of deckbuilding. I hate cutting.
Disenchant: if you run Seal of Cleansing
Norn's Annex: This is a great pillowfort card, but I would rather have Dictate of Erebos, Seal of Removal, or Ophiomancer
Crawlspace: for Silent Arbiter since the arbiter can feed Ertai.
Also, it would be hilarious to run Dovescape.
I'd have waited until I saw a need to use the tutor instead of establishing immediate board presence. I'm pretty patient when it comes to tutors, but I also try and get a lot of value out of them.
Also important are the chances of you acquiring another black mana source, when you will ideally need it, etc.
Typically though, I look at a card like Vamp tutor and see a card that if used properly will win me the game.
This is nothing more than poor threat assessment. It's really no different to me than someone 'geddoning when someone else has a better board state. I find people's absolute hate towards symmetrical advantage interesting and somewhat irrational. I get it if a player has no intention of winning, but every card named in this thread can be used as part of a legitimate strategy.
For example, I've played extensively against a Kami of the Crescent Moon deck loaded with symmetrical group draw. People think it's stupid until they all lose to that deck, which happened often as the deck was well constructed and the pilot knew what he was doing.
However, if someone is playing any deck/strategy that has no intention of winning, then I find that it is perfectly reasonable to get annoyed.
It would probably be much easier to set a restriction like: "Commander deck has to be built from Standard-Legal cards only".
As you can see by the responses in this thread, opinions vary as wildly on cards as the people and playgroups using them.
As far as house-bannings, I think the best way to approach banning cards is by group consensus and on a case-by-case basis. This also requires you to have an established and like-minded playgroup.
Pay 2, sac Wayfarer's Bauble fetching a basic, trigging Omnath's ETB for a 5/5 elemental, triggering Parallel Lives for another, tap Salvaging Station to bring back Wayfarer's Bauble, sac a 5/5 to do 3 damage float 3 mana and untap Salvaging Station, sac the basic to Squandered Resources floating another mana, crack Conjurer's Bauble putting the basic back into your library and drawing a card, tap Salvaging Station to return Conjurer's Bauble to the field, rinse and repeat until you deck yourself, or kill everyone. You will need 2 5/5 elementals to sac after using the initial Salvaging Station activation for each loop.
Laboratory Maniac is probably better than the angel here as there is the possibility of winning the game with him before enough damage is dealt to your opponents, making him slightly stronger than Platinum Angel, though you can technically do infinite damage with the angel out.
You do end up with an excess of mana this way, and the combo can obviously be sped up with damage doublers, additional token doublers, more landfall token generation, ability copying effects, etc.
Enchantment
Surge
Sorcery
Return target colorless card to its owner's hand unless they distribute 5 -1/-1 counters
I run this in more decks than I care to admit. People just never see it coming.
It's a really crappy-looking, budget deck with fogs, garbage like Vow of Flight, Assault Suit, pillowfort stuff like Sphere of Safety, stuff like Finest Hour (it's a one-shot with Karona...) and some cheap ramp.
I don't play it very often, but it's really fun.
I guess if you want that card just buy the precon.
Legendary Creature - Spider
Reach
Creatures you control assign combat damage equal to toughness instead of power.
: Belbeth deals damage to target creature with flying equal to Belbeth's toughness.
2/8