I personally adore janky combos. They're basically half the fun. So... what are your favorites?
A couple that I've thrown together recently:
Generous Patron + Proliferate: This basically reads "draw X cards whenever you do [blah], where X is the number of creatures your opponent's control with counters on them". I like doing it with +1/+1 counters, because I'm "nice".
Fertilid + Amulet of Vigor + Evolution Sage: This gives you ": Search your library for a basic land card, put it onto the battlefield, then shuffle your library. Proliferate." If your mana base is primarily basic lands, this can almost double your lands every turn (If you start with X lands, you end up with 2X-1).
Simic Guildmage + Hapatra, Vizier of Poisons: Generate a snek for . More usefully, you can then spend to remove a -1/-1 counter from your guys and get a CIP/death trigger (dump the counter on a snake token, get a new snake token).
Throes of Chaos + Harness the Storm:You get anywhere from two spells to six spells for every land card you discard, depending on what else is in your graveyard. I think I'll be building this deck when Modern Horizons comes out... Each land turns into 1-4 random spells with CMC 3 or lower, depending on how many Throes are in your graveyard. I was misremembering Harness the Storm there. The only reason this is more impressive than it'd normally be with retrace is because you get double storm count.
This isn't exactly a combo but in my Jodah EDH deck, I once cast a Howl of the Horde (with raid) with mana from a Primal Wellspring and I cast Worst Fears (everything for free due to Omniscience), so I effectiely stole my friend's next seven turns. The best part is that the deck is entirely built from draft chaff and random boosters I bought.
"Reading the card explains the card." -Tolarian Community College
Now, normally, I hate TakingTurns.archetype, but this, I love. Why the seeming dichotomy, if not outright hypocrisy? It's because Taking Turns usually starts going off around turn 4 or 5, whereas Dinos with Helmets can only ever go off like that post turn 8 or so, more than enough time to guarantee interaction, one way or another.