Cryptic Trilobite has at least two +1/+1 counters on it.
Gilder Bairn does not have summoning sickness.
Mana Needed
({2} magic symbol) available.
Steps
Activate
Gilder Bairn by tapping it, adding ({GU} magic symbol) .
Activate
Gilder Bairn by paying ({2} magic symbol) ({GU} magic symbol) and untapping it, doubling each counter on
Cryptic Trilobite.
Activate
Cryptic Trilobite's first ability by removing a +1/+1 counter from it, adding ({C} magic symbol) ({C} magic symbol) that can only be spent to activate abilities.
Repeat.
Once you have infinite +1/+1 counters on
Cryptic Trilobite, you may instead double the counters on any other permanent(s).
Results
Infinite +1/+1 counters on a creature.
Infinite colorless mana that can only be spent to activate abilities.
Infinite proliferate.
Metadata
In 10 decks according to EDHREC.
Bracket Tag
This combo has been estimated to be Exhibition (Bracket 1+).