generation 2

Thats an easy one...Tyranitar.

Lugia for gym defense.

Lugia probably won't be accessible for a while, and tyranitar will show a bunch, but weakness to water and grass will make him easy to knock out. I bet we'll see kingdra and feraligator quite often, with the occasional amphoros

defense, none.
offense, Kingdra.

Honestly I don't think the gen 2 will bring some top tier defensive pokemons. I can just think of Lugia...
I will bring some good attackers tho.