I prefer the EtherKiller.
Somebody actually rigged a RJ45 port to feed raw 220V into the Ethernet port. There is also a version for IDE interfaces. So simple, so lethal... so beautiful. Like a sledgehammer applied to the back of one's hand caught stealing in the Blackjack table at Las Vegas.
Things of beauty. Raw, unadulterated justice to the luser that keeps demanding free repairs and maintenance.