Scout. Yeah he might be small and fragile, but man, do I kick some ass. Soldiers trotting around with their rocket launchers thinking they can out-do me. Wrong!

I play a mix of Soldier and Scout, mostly because I love their unlocks.

Scout > Heavy > Medic

Alright, I play mainly as the engineer but i have recently been playing as the medic. I know, Both are "cowardly" classes. but to be honest i like the option of healing(MediGun) and Shooting(SyringeGun) that the Medic has to offer, and the option of having a defensive(Sentry Gun) strategy and also an offensive(Teleporters) strategy. But, thats just me.

Demoman!

Due to the WAR, my most played class is soldier, but I haven't played him a whole lot since. Pyro and Heavy.

I switch which class I play based on what the rest of my team is playing as and doing. My favorite class to play as is pyro, but lately I've been playing as sniper and engineer a lot.

Damn. I can't select them all.  
 
I have no preference, it's just what I'm feeling that day. Some days I like to play as Medic and Engineer, and help out. Others I just like to go balls out and run in, get a quick kill, get the intelligence, get dominated and repeat as Scout.  
 
Others I just like to sit and press MouseButton1 as Heavy. 

My 'time played as' for the Pyro, Spy and Sniper are all almost the same, but Pyro beats them both, followed by Sniper, then Spy

almost always Sniper, i love sniping in games and this is no exception. I often play as the engineer as well and occasionaly the heavy

I like Soldier the best because it reminds me of straight up Quake, but I play Pyro when the other team is fielding tons of Spies, just because I love pissing off Spies.

I'll use em all I guess, I prefer the Sniper, Scout, Spy and Medic though.

I usually play the sniper but I switch around if its needed.

Competitively I play Medic, but when messing around on Public I like to change it around.

I've been really enjoying pyro recently - but I found the whole needing to get closer range thing annoying.

I main Scout, but I also frequent Sniper, Soldier and Engie.

I am a career spy. 
I also go medic and sniper when I need too. So mostly I play support.

" I generally play as pyro. And quite often the heavy. "

Soldier, all the way - not been playing much recently, though so I'm pretty shit at playing Soldier these days. :(  I'd like to get good enough to the point of pickup/clan games or something though, cause they're fun in TF2.

Demoman. Blowing all sorts of shit up

i play as pyro, i hated him when i first got the game but now ive mastered him.

I pretty much play all of them,though Sniper and Spy less often since I suck as them:P.I've logged the most time as Heavy but I've got the most points as Soldier,think it's the class I'm best at but I only use it when attacking.

" Spy or Sniper (The update was good for me :) ) and a little bit of Heavy, I hate anyone who plays Pyro though, considering it's the easiest class to play in the game. I'm hear to start a flame was (Oh the puns) So yeah, Pyro is the easiest class to play and is the noobiest class. In order to be successful you spam your flamethrower and run away. You only die if it's someone out of reach such as a sniper. You yourself can't get lit on fire and you have a flaregun for dealing with those pesky snipers too >_>. Pyro's need to be nerfed (Flamethrower overheating anyone?)Someone prove me wrong. "

Wow! I'm amazed at how even the poll is! signs of an excellent class based multiplayer :D

Started off as Soldier when the game was released, but play pretty much exclusively as a Scout these days. Running around, annoying the opposition is really satisfying. I wanted to get better with the Spy, but I just can't get get used to him.

Mostly Spy with the cloak and dagger, I like to hang out near the enemy spawn and take random shots at people in between sabotaging stuff to make the enemy team constantly paranoid that a spy is lurking around their base. Pyro would be a close second.

Pyro.
 
Spammable flamethrower, flare gun sniping, blowing people ;]

Pyro. 
 
 
 
Burning stuff is fun.

Heavy, because my computer isn't quite good enough, making precision a bit of a bitch at times, and I'm awful at using a mouse and keyboard for FPSes (yes, I know; it's crazy, but it's true) which results in even more problems. I basically can't play Engineer or Spy effectively with this setup, which is amusing because, on the 360, those are my two best classes. *sigh*
 
On a related note, while I'm here, I'd just like to apologize to the late-night citizens of the GB/Tested TF2 server. I love the game, and I try my best, but my pretty decent skills on the lame console version do not (yet!) translate to the PC version. I'm sorry for sucking, and thank you for not chewing me out (that I've noticed, anyway). (My Steam ID is "Sharptoid", by the way. Yeah, that guy.)

I play Soldier with default weapons the most and Spy with default weapons as backup. Sometimes I play Scout when on a 5 CP map.

" I've been really enjoying pyro recently - but I found the whole needing to get closer range thing annoying. "

Spy all the way, no other class delivers the same experience and tension.

" Spy all the way, no other class delivers the same experience and tension. "

" I use all of them except Demoman. I just can't get a hang of his weapons at all. "

" @mubblegum said:

" I've been really enjoying pyro recently - but I found the whole needing to get closer range thing annoying. "

Flare Gun, My Dear, Flare Gun.   I'm a Career Pyro though.  I can hang back and ping guys with the Flare Gun, support the Engies by spychecking or smashing Sappers, be the secondary medic by extinguishing teammates, OR just burnin shit.  I love the Pyro. "

 Medic is my most common since a good medic jumping on a team can swing a game more than any other class and there's usually a lack of them.  Plus there's nothing like being on the front lines and keeping 3-4 people alive long enough to hold a point.
 
If there are enough medics or I get bored, I'll play anything but spy or sniper.  Pyro has become my new alternate go-to and Scout works will for pub servers where teams don't know how to set up defenses properly.

I generally play the pyro though will play  anything if its lacking in a team.

Scout for me, its all about the offence and capture of points/Intel

I voted Scout, but only because its my most played class by stats. 
 
I like Heavy and Pyro much more than the Scout, but the latter is leading about 5 hours to the pyro (49 vs 44), followed by Heavy with only 20 hours, which is a really weird gap because I love that class.

sniper

Engineer all the way man. Started playing as the Heavy recently and i like him, so fun to go in a room filled with those damn reds and just hold down the mouse button and say to myself  "AAAA I'M SHOOTING! AH NAH MY HEALTH! *Blap* *Dead*"

My play time is pretty evenly split between sniper and engi, with a slight lead going to the sniper. It just feels the most comfortable coming from traditional shooters. The engi is just a bamf, no explanation needed.

Sniper/Heavy.

heavy, medic, and pyro. but medic the most.

Sniper, engie and recently I've been doing well as the scout. I'll play whatever needs to be played really except the demoman, i can't  acclimatize myself to his arsenal.

Sniper if possible, otherwise Soldier.

I play sniper, pyro and medic more than any other class. I agree with MattyFTM, pyro is easiest class to pick up and play good off the bat but a truly great pyro takes skill.

Cuh-Rit! Soldier is my most played. Followed by Engie. Then medic/scout. Everything else I barely touch.

Soldier, Sniper, Spy, Medic