Worldgorger Dragon + Animate Dead. This also requires 1) permanent(s) that tap for all colors of mana without etb'ing tapped or causing damage, like say a Command Tower, or an Underground Sea + a Plateau; 2) dragon already in the graveyard; 3) another creature in some graveyard to end the infinite animate loop or an instant that lets you get one there. Mana cost: is 2 mana at minimum, more like 6 mana on average (resolve 2 tutors at an avg of 2 mana each, resolve Animate Dead = 6 mana). Pros: very fast. Winning the game after spending a total of six mana is very fast, which is the main benefit. Also synergy with general reanimator strategies and Ad Nauseam. Slots required: 6+ ? There's the dragon, 3-ish animate spells, 2-ish deck-to-graveyard tutors, some restrictions on the manabase, probably also requires running more than average number of looting effects. Cons: if interrupted will exile all your permanents; vulnerable to GY hate.
Auriok Salvagers + Lion's Eye Diamond. Mana required: 4-8 range: 2 tutors, an animate dead, one activation of salvagers. Can also just cast Salvagers for 4, activate for 2. Slots: 2, basically, just the salvagers and the diamond. Pros: Can also benefit from the reanimation spells and deck-to-graveyard tutors since putting diamond in the GY is good; reanimating salvagers is cheap or mana-neutral. Cons: discarding your hand makes protecting this combo with counterspells sort of impossible, requires running something like grand abolisher or silence. Vulnerable to GY hate.
Doomsday / Laboratory Maniac. Doomsday itself works fine for setting up dragon or bomberman combo, if you include Thought Scour. But doomsday can also set up the typical labman wins. Slots: 2+, doomsday and labman; also requires draw and filtering cards, but those are probably included anyway. Lab man can also win off Notion Thief + Windfall
, or just Tainted Pact, which are likely value includes. Mana required: 4-6+ ? 3 for doomsday, 1-3 for a draw spell, 3 for labman, maybe -3 for including Lion's Eye Diamond in the pile. The downside is all that mana is needed on the same turn to assure the win off Doomsday. Pros: Can set up piles that don't use the graveyard; although they're more mana intensive. Good synergy with bomberman and dragon combos. Cons: getting the doomsday pile disrupted loses you the game.
Ashnod's Altar / Krark-Clan Ironworks + Eldrazi Displacer / Nim Deathmantle. This combo works by sac'ing Breya and/or her thopters for colorless mana and then bouncing Breya in and out using displacer or deathmantle. Slots: 2 at best; 4 for redundancy. Mana required: Breya has to be in play for this one since it generates colorless, so there's 4 for breya + 3 for ashnods + 3 for displacer = 10 mana. If you add 4 for two tutors under the typical scenario, then that's 14, split over multiple turns. Pros: Ashnod's + Displacer doesn't use GY; these combos don't immediately lose the game if they're interrupted. Cons: sort of minor synergy with other cards likely included in the deck.
Dramatic Reversal + Isochron Scepter. Just play out enough rocks and this is infinite mana. It's hard to get infinite mana of all four colors, tho, unless you have mox opal / mox diamond in play (or something like prophetic prism or prismatic lens). Slots: 2, but also requires a critical mass of mana rocks (10+). Mana required: 4. Two to cast the scepter and 2 more to activate it; assuming 2 tutors that's 4 + 4 = 8 mana. Pros: there's some synergy of scepter with other 2 mana instants, it's possible to stick a tutor or counterspell on it. No real loss if this combo is disrupted. Not reliant on graveyard. Cons: minor lack of synergy with dragon / bomberman combo; otherwise none? It's a very clean combo.
Sunrise Eggs. This combo runs Codex Shredder to repeatedly get back Second Sunrise or Faith's Reward along with artifacts that sac themselves like Darkwater Egg and mana-positive rocks that sac to Krark-Clan Ironworks. Slots: like 11+? 1 Codex Shredder, 2 sunrise/reward, 1 ironworks, 4-8 eggs. Mana required: 5 for codex shredder, 4 for ironworks, 3 for sunrise, 2 per egg for 3-ish eggs: 18 mana? Functionally less since you're sac'ing eggs for mana to cast the other stuff. Pros: synergy with deathmantle / displacer combo; bomberman combo; low cost of interruption. Cons: vulnerable to GY hate; low synergy with dragon and doomsday.
Thopter Foundry + Sword of the Meek + Ashnod's Altar / Krark-Clan Ironworks. This generates infinite flying 1/1's and infinite colorless mana. It's possible to do this at instant speed, untap, and attack for the win with infinite 1/1's. Or if Breya is in play, you can use infinite colorless to activate her sac'ing the infinite 1/1's to burn out the table. Slots: 3-4. Mana required: 7 to cast the three pieces, 1 for the first activation of foundry, plus probably 6 mana for 3 tutors, for 14 mana on average to tutor all three pieces, put them in play and kick off the combo. Pros: synergy with other Krark-Clan Ironworks combos. Cons: is actually a 3-card combo instead of a two-card combo; dissynergy with dragon/bomberman combos; vulnerable to GY hate.
Pili-Pala + Grand Architect. This generates infinite mana of any color; they just have to both be in play and Pili-Pala needs to not be summoning-sick. Mana required: 5, or 9 with the typical two tutors. Although note that architect can tap himself to cast Pili-Pala, even while summoning sick. Slots: just 2; can also benefit from the reanimation and deck-to-graveyard tutors. Pros: synergy with reanimation strategy; otherwise doesn't actually use the GY. No real cost of interruption. Cons: reliance on fragile creatures, would benefit from haste.
Dualcaster Mage + Ghostly Flicker. This 2-card combo generates infinite colored mana provided there's a permanent in play that taps for each color (just like Worldgorger Dragon combo); or just wins at instant speed if Breya is already in play. Slots required: just 2, really. Mana Required: 6, all at one time. Probably another 4 on earlier turns for two tutors to get the pieces, for a total of 10. Pros: pieces mostly useful apart from the combo as reactive spells; low downside to getting the combo interrupted, not dependent upon the GY. Cons: lack of creature tutors to get Dualcaster Mage; lack of real synergy with other combos.
So,... This shows why we like Worldgorger Dragon and Bomberman. 2 mana is not very much for a combo. It's way better than some other combos that cost 10 mana. :) Other than that, we'd like to have a win that wasn't graveyard dependent, so we're trying Lab Man for now.