As there's a thread like this in the Diamond/Pearl forum, I won't repeat the recent happenings there. But I did play Colosseum for the first time in quite a while yesterday. I just trained my best Pokemon team in Mt. Battle (areas 6-8), and now they're just above level 50. My team currently consists of:
Poppon (male Jumpluff), level 52
Nature: Calm
Ability: Chlorophyll
-Synthesis
-Sleep Powder
-Cotton Spore
-Mega Drain
*I usually have Poppon first in my party (although he's usually switched out or KO'd at the end), and most of what he does in battle is put foes to sleep. Sometimes he also uses Cotton Spore to make it so that my other Pokemon can attack next. His high Speed really comes in handy.
Plusle (female Plusle), level 52
Nature: Bold
Ability: Plus
-Charge
-Spark
-Fake Tears
-Encore
*She doesn't have a nickname because I received her from Duking. She's an attacker/helper. Often times she will use Fake Tears so that my other Pokemon can do more damage with a special attack that turn. She hardly ever uses Encore, but it comes in handy in rare cases.
Nuo (male Quagsire), level 51
Nature: Hardy
Ability: Damp
-Surf
-Earthquake
-Mud Shot
-Amnesia
*It helps that I have three Pokemon who are unaffected by Earthquake, and one who's resistant to it. Nuo has Mud Shot as a backup just in case he has to battle alongside Plusle, or if Skeeter's low on HP. I find that he hardly ever uses Amnesia, though...
Miyage (female Delibird), level 52
Nature: Relaxed
Ability: Vital Spirit
-Present
-Attract
-Fly
-Blizzard
*I like using Blizzard here because it's powerful and hits both foes, and also because it can freeze. I know Present's kind of lame, but I can't find a good attack to replace it with...
Voldemort (male Misdreavus), level 52
Nature: Lonely
Ability: Levitate
-Psybeam
-Shadow Ball
-Pain Split
-Perish Song
*I like to send Voldemort out when my opponent is down to their last two Pokemon, so there's no chance of switching out. I especially like to pair him up with Nuo or Poppon--it depends on whether I want to do a lot of damage quickly or stall while Perish Song counts down.
Skeeter (female Heracross), level 53
Nature: Hasty
Ability: Guts
-Endure
-Reversal
-Brick Break
-Megahorn
*Skeeter just learned Megahorn yesterday; before that, she knew Counter, which was practically useless. I find the Endure/Reversal combo works well on someone with high Attack.
I'm probably going to get my team to level 55 before continuing in Realgam Tower.