Infestation traps a pokemon in battle and takes an 8th of your health a turn, add toxic poison/burn and you can troll everyone.
That's why I added RegiSTEEL and Lucario. Unless Shuckle is a rebel and learns to smoke so that he can throw its cigar to the opponent and burn it. And Terrakoin pretty kills it fast. However, you can always change to another Pokémon if it is necessary.
Pokémon that I am conflicted over... Bronzong. Yes, it is now immune to
yet another trap and walls Fairies and Poison types and Ground types, but... the buff of Dark and Ghost... and it's so darn hard to breed (to one hundred eggs and all I got is a 31/31/31/x/31/x). Y U NO GROW PEE THINGY!