Sonic the Hedgehog Series: Made me a SEGA fan and a Sonic fan even if they are not properly using the license now. Also caused me to have a craving for fast-paced games.

Threads of Fate: Not sure how well known it is, but it made me a permanent Square fan forever cause it was an RPG with an entertaining story and colorful characters that was still fast-paced and caused me to get back onto the RPG scene.

Counter-Strike: Taught me that online FPS's are not nice places and that there is a limit between playing videogames for fun and making them your life.

Halo 2: Caused me to truly hate playing with little kids online.