Either with complex event systems or on the technical side of things, who has shown a knack for pushing the engine? Note that this is not for scripting!
Providing screenshots / links or other examples may help your nominee's chances!
modernmath
Zylos
flapbat (farmyard chronicles)
Yuyu. She's evented a pretty robust farming system, along with a system for moving NPC's around on a schedule.
yuyu, modern and sophist