And I can't decide what form to give it.

It knows Discharge, Ominous Wind, Dark Pulse and Confuse Ray. I'm thinking I'd replace Dark Pulse, even though it does eliminate a weakness against Dark types and so it doesn't really matter if I swap around the forms. Okay! I'm thinking that Leaf Storm would be good, it would eliminate the weakness against Ground.

MOW ROTOM AWWWWRIGHT

edit: Stats before change:

hp / attack / defense / sp attack / sp defense / speed

131/85/118/149/107/122

Stats after change:

131/102/157/161/141/117

woah, speed drop

real shame, but the high special attack is worth it B)