How about this?
Thunderpunch(egg)-covers water weakness
Blaze Kick(Egg)/fire punch-STAB, good power
swords dance(TM)/fake out-powers him like crazy, or fake out, since it is LC.
brick break(TM)/vacuum wave-cover rock weakness, VW is priority, making it even better.
Heatwave/flamethrower/fire blast/overheat-Your choice, heatwave is in the middle for power and has no bad secondary effects like overheat, (I like overheat since chimchar will only last a little while anyway. Plus using overheat after blaze activates is fun.)
Grass knot/hidden power (grass)-both moves cover all of chimchar's weaknesses. if you can't get hidden power, grass knot works too. Unfortenately, since the little cup pokemon are typically small, grass knot loses it's charm, which is why hidden power is probably the better option.
taunt-force the foe into attacking. good for breaking your opponent's walls.
Fake out-I know it's physical, but this is LC.
Other good moves: