Show Only Guru Approved Combos
Baral's BioweaveBiovisionary Buy + Baral's Expertise Buy + Mirrorweave Buy
Thought this was interesting idea to help ensure opponent doesn't have enough creatures and I'm pretty sure you can come up with some token generation using green/blue to go with this.
Nissa's ShepherdEmeria Shepherd Buy + Nissa, Genesis Mage Buy + Doubling Season Buy
I found this as a weird engine that requires some pretty hefty fuel to continue, but makes a very neat interaction. It isn't infinite by itself, but you can more or less repeat it every plains you get for free and it costs 7 mana to repeat. It kind of looks like this:
: Ult Nissa, if a plains hits, repeat this process, if a non plains land hits, return Nissa to hand.
Get the LandsRetreat to Kazandu Buy + Fertilid Buy + Stone-Seeder Hierophant Buy
The only thing that is needed is a land that can produce 2 mana, then remove a +1/+1 from Fertilid, put a land into play, put a +1/+1 counter onto Fertilid, untap land with Stone-Seeder Hierophant, then repeat to get all the lands.
Ministrant DeathmantleMinistrant of Obligation Buy + Nim Deathmantle Buy + Ashnod's Altar Buy
Just stack the triggers correctly to get infinite tokens and infinite colorless mana. Deathmantle is a broken card, I know.
Hadana's WeaverHadana's Climb Buy + Spike Weaver Buy
Pretty sweet eternal fog
Codex of BrighthearthCodex Shredder Buy + Rings of Brighthearth Buy
It's fairly expensive, but meant for any EDH deck as an alternate means of recursion.
1. Sacrifice Shredder to return a card. Trigger Rings.
2. Pay Rings cost to copy Shredder ability, target Shredder.
3. Shredder returns to hand, then initial activation returns other card to hand.
4. Cast Shredder. Repeat as desired.
Net: : Return target card from your graveyard to your hand.
Some Old Dogs(cards)but w/ New Tricks (Rules Text)Portcullis Buy + Wormfang Crab Buy + Mulldrifter Buy
Thanks to improvements on wording over the years, Portcullis Buy becomes clearer to read, and how it works has become easier to understand.
With 2 other creatures in the battlefield(not necessarilly yours), evoke Mulldrifter Buy, and the like, get the etb effect, then exile them w/ Portcullis. Then we cast Wormfang Crab to "flicker" Portcullis. This lets you get another etb and ltb trigger from any cards exiled w/ portcullis.. which includes Wormfang Crab. Rinse, Repeat.
Scout Coralhelm Growth ChamberRetreat to Coralhelm Buy + Llanowar Scout Buy + Simic Growth Chamber Buy
Have the Llanowar Scout in play with the Retreat to Coralhelm. Play a land for turn, then tap Llanowar Scout to put Simic Growth Chamber onto the battlefield, let the Retreat to Coralhelm untap the Scout and put the land you just bounced into play. Repeat this with a second Simic Growth Chamber or other bounce land for lots of landfall triggers.
Pauper Infinite Red ManaSafehold Elite Buy + Ivy Lane Denizen Buy + Thermopod Buy
Project X in Gruul??
Infinite IncubationVigean Graftmage Buy + Incubation Druid Buy
Have Vigean Graftmage in play, and summon Incubation Druid, placing a +1/+1 counter. on it. Incubation Druid taps for 3 blue mana, and untap it with Vigean Graftmage for 1 and 1 x blue mana. Rinse and repeat.