I'm more of a Scout player right now, but that's because I'm trying to earn the milestone achievements (I've only played about 8 hours so far). I also enjoy playing the Sniper, Soldier or Demoman depending on the situation.
Demoman is definitely my favourite, his stock weapons are all I need. I just got my hands on the Sticky Jumper... I have no idea how to use this weapon.
Er, it's not supposed to be a weapon. It's just there so you can practice your sticky jumping in a private match, just like the Rocket Jumper.
@moopus It's not as great as you think. Crits don't affect sentries, so have fun getting torn up when you try to enter an enemy base. It can be pretty good in Payload maps though.
I like Scout the best. Even though I haven't played TF2 for more than a year now, and I don't plan on going back. I only played on my clan's 2Fort server, and I was the best at capping the Intel. I got really good at using Bonk and the third jump you get from shooting the FaN downwards in the air. Good times. Although I spent about 75% of my time as an Engineer because no one seems to like being an Engie on 2Fort. It's a boring thankless job, but somebody's gotta do it.