If this means "a character I have seen in action" or something along those lines, I would choose either our cleric or rogue in our current FR campaign. The dwarf cleric is tough, punishing, and versatile. The halfling rogue is a killing machine (assuming he can gain sneak attack position) and stealthy as a shadow on a dark Halloween night.
If this means "a character I have yet to play" then I would choose (from 3.5) a monk or a druid. I'd really like to see a monk in action, and same goes for a druid. Hmm, a druid with an animal companion, a summoned animal ally, and the druid in wild shape form. Now THAT seems like something I could have fun with.