If you want to increase the tension and suspiscion levels, I highly recommend passing notes and having "private meetings". If they don't start with the notes, hand one to someone. It can even be blank. Or it can say something evil and spurious about another player...
The more that the players feel like Player A knows something that Player B doesn't, or that Player C just went off with a suspicious looking character, the more likely they are to do your job for you.
Randomly yell out, demanding a decision -- if they hesitate, say the are caught in a crossfire, under a falling foodvat, whisked away by a rampaging funbot, whatever...
Force people to switch chairs depending on how In or Out of favour they are with you (The Computer); have one less chair than necessary, thus forcing one player to stand (and/or act as the maid for the rest of the group until he regains your favour).
In other words, do all the things you ever wanted to do to players in the past, but felt you couldn't because it would look like you are being "unfair" or "showing favouritism".
And providing odd looking munchies for the game (strange colours, odd shapes) really helps get folks in the mood, too
