Sometime in TF2 I assume. I have no idea, but there's a shitload of good moments lying around.
Actually, just a couple days ago I decided to try and use my pen tablet to play it. Unfortunately you have to hover the pen in the very middle and move it where you want to turn, so it's not relative movement and INSANELY hard to control. So I made it to the far side of the 2Fort bridge as Soldier, two enemies dropped on my head, my pen spazzed, I fired at the ground and killed them both with a crit.

Actually, just a couple days ago I decided to try and use my pen tablet to play it. Unfortunately you have to hover the pen in the very middle and move it where you want to turn, so it's not relative movement and INSANELY hard to control. So I made it to the far side of the 2Fort bridge as Soldier, two enemies dropped on my head, my pen spazzed, I fired at the ground and killed them both with a crit.