#25 - Team Fortress 2 (PC)
As guessed by Ganoncrotch! TF2 surprised me in an increasingly surprising Orange Box by being an insanely addicted, lightweight yet deep, customisable and brilliant first person shooter. Perfect to play over Steam with some friends, the class-based system just works so perfectly with each being strong against some but weak against others, with a good player being able to take on all comers. Really enjoyable and something I still play regularly to this day.
Clue for my #24 - European PS1 launch title featuring a robotic rabbit in crazy first-person-platforming antics.