Cascoon

Stats
Shed Skin: 30% chance to recover from status at the end of each turn. HP:
50
Atk:
35
Def:
55
SpA:
25
SpD:
25
Spe:
15

Walling Cocoon

Item: Leftovers Cascoon is one of several standard cocoon wall with limited capabilities. Bug Bite is your primary attacking option, with String Shot being potentially useful for lowering speed and Iron Defense possibly helping in a stall war with a physical sweeper. Poison Sting doesn't hit anything harder than Bug Bite, but carries a 10% chance of poisoning (oh joy). Snore is also a potential option to allow Cascoon to do something in the way of absorbing sleep. If you go with Snore, you can consider switching to a Relaxed nature in order to do a little more with it, as you won't be outspeeding anything anyway.
Nature: Impish / Relaxed
EVs: 252 HP, 4 Atk, 252 Def
Moves: - String Shot
- Bug Bite
- Iron Defense
- Poison Sting / Snore

Other Options:

Cascoon's other options when it comes to moves are limited to Harden, which is outclassed by Iron Defense, and Tackle, which will never hit as hard as Bug Bite against anything. Stick with some combination of the above moves.

EVs:

Cascoon is a wall and should be treated as such. Focus primarily on its HP and Defense with your investment. What Cascoon has going for it that the other cocoons don't is its decent base 35 attack. Any modifications to its EVs should focus on increasing attack, as this is what makes Cascoon different. If you want speed, go with Metapod or Kakuna.

Counters: