I first got into the hobby back in 2000 when Dungeons and Dragons 3rd edition hit the shelves. A friend invited me over for a game and I was hooked immediately. Ever since then I've refereed for players using all of the Dungeons and Dragons editions, d20 Modern, GURPS, Fate and Shadowrun. My absolute favorite games to run are the OSR clones of Advanced Dungeons and Dragons, most especially OSRIC and Labyrinth Lord. GURPS 3rd edition is a very close second due to its flexibility and complexity, but apart from all of these I also write my own systems, which I will play test as soon as I get off my lazy ass and finish them :)