It's a bit gimmicky with its ability; I recommend a SKill swap set: I love trachy's.
Skill Swap: I hate the ability Color Change. It is Kecleon's weakness. It also helps with the strategy I have.
Aerial Ace: Decent power, doesn't miss, deals with Fighting types. Makes the foe a Flying type my strategy.
Rock Slide: The foe is now weak to this. Used to deal with Flying types. Decent power, decent accuracy, good chance to cause flinching. Makes the foe a Rock type.
Brick Break: The foe is now weak to this. Used to deal with Rock types. Decent power, high accuracy, breaks through Reflect and Light Screen. The foe is now a fighting type and weak to Aerial Ace.
The spot guy. Really good with Contrary, as Superpower Contrary gives it a Bulk Up boost, plus a good attack.
Spinda (F) @ Focus Sash
EVs: 252 HP / 4 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Fake Out
- Rock Slide
Mew's moveset, but only contrary.
Overall, neither of them are very good; however, Spinda is probably better.