Each member on my team must have something (other than looks) that makes him "unique"
I mean a pokemon like masquerain is pretty cool, but it's moveset (Bubblebeam,Giga Drain, Ice Beam and Silver) doesnt really help my team, As I already got a A flygon and a Walrein who outshine his offensive capabilities.
I like hard hitting Pokemon, most of the times physical attackers. I usually don't mind slow pokemon, as long as they're bulky, like Swampert and Blastoise. I also like Sword dancers like Zangoose (who learns it at a ridiculously low level) and anybody that can learn it by breeding it with zangoose (most often being Sandshrew, I'm talking 'bout Hoenn here)
Sometimes I tend to picky about natures, as I REFUSE to raise a modest Breloom!!
Also I'm usually havin trouble to find myself a FLY user, as I always used Fearow in Kanto/Johto, Flygon in Hoenn and Staraptor in Sinnoh.
I never use HM slaves, well not as a member of my team, If I need Cut, I get a cutter and deposit him back at pokecenter in the next town.