Man he's got high attack! this guy is like a mini Rampardos! Anyway his best stat is obviously his attack, and all his other stats aren't that bad for little cup...except that 10 speed. You could use trick room if you want, or invest a few EVs in his defenses. But here is my suggested set:
Earthquake(TM)-Powerful move, STAB, physical, perfect for Trapinch.
Bug Bite (egg move) -physical, 60 base power, covers his grass weakness, it'll do quite a bit of damage to any little cup pokemon coming off of his attack. It also takes the effect of your foe's berry, and berries are a lot more common in the little cup than they are in standard play.
Rock slide(TM)-Physical, covers ice weakness
quick attack(egg move)/sandstorm (TM)/Return /(TM)-Quick attack as a priority move, sandstorm for added damage, or return for a pretty powerful move.
This is my set for little cup, but if you don't have any limits set, I'd use this set:
Earthquake-same as above
Bug bite-same reason as above
Rock slide-Same reason as above
Crunch/Quick attack/sandstorm-Crunch for more type coverage, quick attack for a priority move, or sandstorm for added damage.
To me, Giga drain seems pointless to put on him, his special attack even in the little cup world, is pretty low, so it defeats the purpose of putting it on him if it can't KO any water pokemon.