That's a quote from JoyStiq. I'll take it as a personal challenge, and I think it's a worthy one. I suppose it could be expanded to all kinds of media, but let's start with games.
My young life is a mishmash of games, many of which were video games. If we're not talking video games, "Clue" was actually a big influence on my gaming ideology... but let's stick to video games.
Obviously, System Shock II was a massive influence on me. In every way it influenced my thinking. Perhaps due to an early predeliction towards sci-fi, I haven't yet seen another game whose situation caught me so much as System Shock II. The influence can be plainly seen in all my works.
The other major lynchpin was Final Fantasy, the original. It's not my favorite Final Fantasy, but it is the one which affected me most. For starters, it totally set me up to get memetically hosed by System Shock: on a fundamental level, the two games are very similar. Since I played it with an extremely high fever, the characters in the original Final Fantasy were extremely realistic, and this has since influenced me by guiding my designs towards games with teams of characters rather than solo characters.
Third place could be a very hard call. Ultima Underworld made a big impact on my life, a kind of interim between Final Fantasy and System Shock II. ChronoTrigger, one of my all-time favorites, continually pushes me towards "coming of age" plots and concretes my dedication to parties rather than solos. Zelda, Metroid, and Mario, my old standbyes, definitely pushed me towards a nonrelianiance on stats. I don't much like stats. Maybe it was SimCity - my games all have a tendency towards construction and player content. But I think that's mostly learned from my pen-and-paper years, not from a video game.
In the end, third place isn't a hard call at all. It might be the easiest call.
The Quest for Glory series.
And when you look at my game designs, most of them are obviously trying for the same tongue-in-cheek, fun-yet-grand style of adventure. Most of my games feature the same game dynamic of learning, applying, wheedling, and exploring. As much as my style is slammed into the System Shock groove, in my heart, all games should be Quests for Glory.