[Fox 6]

Hmmm.

I recommend any of these:

Metagross
Hitmonchan (so good learns ice, fire, and thunder punch)
Kingdra (is water/dragon type so its only waekness is dragon itself)
Dragonite
Tyranitar
Garchop
Drapion
Salamence
Vespiqueen


and of course the legendary ones

Girantina
Heatran
andy of the 3 physcic ones or your games diamonds exclusive one.
Some of these guys are only available in pre evolutionary forms and or on pearl only. If youve beaten the game then a new island is opened up with more pokemon and new ones will appear in the old map. Heres something thats also helpful, in your rivals town (cant remember if it also yours) at her/his house their younger sibling will tell you where a rare pokemon is appearing for that day. I cant remember if you have to beat it to unlock that option. Hope that helps.