The first thing I succeeded in making in Garry's Mod. Luigi with the Mask.
Based off of my crossover fan fiction on Fanfiction.net "Mario and Luigi: The Mask"
I have to say though I did not make the models of either Luigi or the Mask, Luigi was ripped from a game I think and the Mask was custom made by someone else who's name escapes me. If I can track down his name I'll edit this discription.