Vedalken Orrery so that you can replay your Omnath after he is killed so you don't lose all that floating mana. Vernal Equinox is an enchantment that is similar, but lets everyone do it. Winding Canyons is a land that does something similar for creatures as well.
Seedborn Muse lets you pump mana into your pool on every other players turn. Bear Umbra lets you get twice as much from your lands and protects your Omnath a bit.
grim monolith and mana reflection is infinate mana..My omnath deck uses infinate stream of life type spells to gain life...and then hurricanes and ifh-biff efreet to kill opponents. With infinate mana you can use cloudstone curio to play and bounce the Eldrazi...thus drawing as many cards as you want, or vindicating as much as you want, or taking as many turns as you want...
Genesis + Yaymaya Elder/Spore Frog
Genesis + Sac outlet (Carnage Alter, High Market) + Terastodon/Solemn Simulacrum/Acidic Slime/Woodfall Primus
Rofellos + 5 forests + Staff of Domination (still good to run him in mono green)
Mishra's Helix isn't really a combo, but it's a dang good use of any extra mana you have.
Good mana sinks are Mishra's Helix, Orochi Hatchery, Wurmcalling, Kamahl, Fist of Krosa, and Myr Matrix.
Vedalken Orrery so that you can replay your Omnath after he is killed so you don't lose all that floating mana. Vernal Equinox is an enchantment that is similar, but lets everyone do it. Winding Canyons is a land that does something similar for creatures as well.
Aluren is much better, ridiculous even, with Omnath.
Since noone's gone for it, and since I've plugged it ever since a kind individual showed it to me, Masticore and Kamahl, Fist of Krosa combine to make LD for 2G per land. Inefficient, but it's repeatable and an acceptable outlet for massive amounts of mana. More outlets for tons o' mana can be found in my Sasaya EDH deck, as that's pretty much what she's good for.
Seedborn Muse lets you pump mana into your pool on every other players turn. Bear Umbra lets you get twice as much from your lands and protects your Omnath a bit.
Patron of the Orochi and Sakiko, Mother of Summer are both strong creatures that give you lots of mana.
Mana Reflection, Gauntlet of Power, Doubling Cube, Vernal Bloom, Heartbeat of Spring, all get you lots more mana.
Another win condition to use all that mana on is Helix Pinnacle. Giving Omnath trample with something like Rancor will usually win faster though.
I've always liked Doubling Cube with Omnomnomnath. Maybe Centaur Glade and Ant Queen for mana sinks?
Genesis + Sac outlet (Carnage Alter, High Market) + Terastodon/Solemn Simulacrum/Acidic Slime/Woodfall Primus
Rofellos + 5 forests + Staff of Domination (still good to run him in mono green)
Mishra's Helix isn't really a combo, but it's a dang good use of any extra mana you have.
Good mana sinks are Mishra's Helix, Orochi Hatchery, Wurmcalling, Kamahl, Fist of Krosa, and Myr Matrix.
On the banning of Mystical Tutor (R.I.P.):
Aluren is much better, ridiculous even, with Omnath.
Standard
GWB Junk Rites GWB
Brewing
GWBU 4-Color Rites/Aggro GWBU
Rules Advisor
+Gemstone Array for infinite G
Driving Stick with Isochron Scepter.
Trinkets and Treasure: An Artificer's Toolbox.
Proc Drops: Playing with One Drops.
Deck Primer: Toshiro Umezawa
B Lover Since '09 ~
Standard:
meh.
Modern:
Urzatron GR
Vintage:
Contol-Slaver UBR
EDH:
Drana B
Jhoira UR
Savra BG
Turned into:
Adun Oakenshield BGR
Sharuum BUW
Turned into:
Memnarch U
KiKi-Jiki R
Turned into:
Godo R
Turned into:
Aurelia RW
The Mimeoplasm UBG
Rasputin Dreamweaver UW
Turned into:
Geist of Saint Traft -French 1v1 UW
Nekusar UBR