I like spiritomb just cuz it looks sooo cool!
but, on the other hand my favourite is Kyogre
kyogre has so many combos!
drizzle powers up water 10%
thunder never misses in rain
water spout, most powerful water move in the game, 150 and it can be used in double battle
SAT means powered up even more
and then there are items you can use to power it up