For me, it's easily t4ils. StillAlive was the first piece of homebrew, and sadly, it set the curve for what I wanted in homebrew, which saddened my, since not much could live up to it. Aside from his brilliant port of portal, I love how he releases his homebrew. Instead of releasing a new version whenever the smallest thing is added, he waits until he has something that the players will enjoy before he updates. Also, I love how he released his finished version of StillAlive before releasing any demos or anything, and then kept building his game up from there. I hate when developers are so excited to get a game released that they put all their effort into a decent demo, and then lose the patience to do anything else.