In Colosseum, I just used my Espeon and Umbreon for the entire game. Not very exciting or original, but it worked well.
In XD, I used Espeon and Breloom. Breloom was my False Swiper/Stun Sporer which helped me to snag the Shadow Pokémon. They were an ok combo, but a little on the fragile side. I went through a lot of Potions/Revives with them two. lol Ampharos was my back-up team member, she was my go-to Pokémon when one of the other two fainted. Basically, those three pretty much did 99% of my battling.