With a couple of colleagues (who fully support, and believe in, my quest to be evil), I came up with a list of things I could do to make the test more enjoyable for the sweating and panicking candidates:
1) staring at them constantly, from about 6 inches in front of their face
2) tapping my pen, every three seconds, on the desk in front of them
3) humming, constantly and off-key (not hard for ToneDeafMe)
4) standing behind them, watching what they were doing and making tsking noises
5) walk into the room, dragging my leg behind me saying "they beat me because i didn't use the correct font. it wasn't as bad as it has been though, they didn't use the stick this time, just the printer cable."
6) having a conversation with myself under my breath along the lines of "you should kill them... no, i'll get found out... not if you hide their bodies in the filing cabinets... but they are papers in the cabinet... perfect to soak up the blood..."...
7) taking the ball out of the mouse before they start
8) waiting til they've just about finished the exercise then "accidentally" cut the power
9) telling them "you've got 15 minutes, start in your own time" then wait about ten seconds and say "ok, are you nearly done? you've got about a minute left"
10) keep looking at my watch and at the door, increasingly frantically, then a minute before the test is finished, climbing behind a bookshelf and say "don't tell them i'm here. i forgot my bulletproof jacket today but these books will be good protection, i hope." then start reciting the lord's prayer.

Needless to say, I did nothing of the sort. Because I'm nice. No, really, I am.

Niceness is really getting in the way of my being evil. Must try harder.