Demo: It's fun to bait people into your sticky traps, and I love getting chains of multiple direct hits in a row, and to get many kills with a single bomb.
Engineer: I love using shotguns, and with 150 hp (gunslinger) and average speed + a short circuit, it's very strong as with enough skill, you can beat any hitreg class, and the short circuit fucks projectile classes.
Scout: He's fast, pisses people off, and the screams of "Of course you use milk, because you ain't aim or win in a FAIR fight." just make me feel wonderful.