I'm a fan of the classics, most of which have been listed here. In Necrum Mines there's a room where you have a blind mudokon sitting under a drill and a slig patrolling round so you quickly have to move the mudokon when the sligs offscreen and then kill the sligs with the drill. Almost every time I do it, half a second
after the slig dies he yells 'What?' I think it's a bit late for that, don't you?
Always makes me laugh.
Slig-slapping is a lot of fun, though I usually do it to solve puzzles where you have to sneak past sligs more quickly: rather than hiding in the shadows and sneaking around when the slig's not looking, you just smack him upside the head and leg it like there's no tomorrow!
In the Soulstorm Brewery there's a secret area which you access using the shrykul after moving some slap-happy mudokons round gates and electric walls. You have a long thin room with a glukkon-teleporter at one end. Once I'd cleared the area of sligs I summoned a fresh glukkon and came down and slapped him. He yelled and ran away and for the next 10 minutes I was chasing him up and down the room while he kept yelling and I was slapping him at every opportunity
. Now that was funny!
Though of course you can't beat the good 'ole
Mysterious Slig glitch from Youtube.