All above are excellent answers, but I will say my personal favorites were Kacey and Jackie. Unlike people like BlueSpike, Kacey and Jackie actually tried to help Chris.
Seriously though, Liquid (for the Father Call and the SingStar challenge videos), Alec (for the whole Asperchu saga) and Clyde Cash for getting Chrissyboy to tardrage enough to make the Don't Mess With Me video.
It's a close call, but I'd have to say Ivy. (Nudging out Asperchu creator Alec Bason Larry by a thin red hair.) I don't know what it was about her that tripped Chris's trigger, but thanks to Ivy we got to see Chris at his crazy-creepiest. I mean, real nightmare fuel like this:
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No just once, but again...
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....and again...
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in a kind of crescendo of creepiness that's genuinely difficult to watch without major medication. Add to that the kind of comic output we haven't seen from Chris since then, (such as the Wedding Special and the (sadly) unforgettable Giant Penis Comic), the House Tour videos that gave us our first glimpse of the hoard, and more gawd-awful singing than I care to remember. Hell, so far as anyone knows, to this day Fat Dummy still thinks Ivy killed herself over him. Now that's some quality trolling!