Video, Mouse) switch is an invaluable tool as it allows one to use multiple computers with just one keyboard, mouse and monitor.
Since I'm the go-to guy whenever there's a busted computer among my circle of friends/family I often have three or four machines sitting in a queue just waiting to be looked at. With a KVM, I can do a complete system reinstall one machine, monitor stability testing software on another and perhaps configure a system which is about to be released.
With a KVM I can greatly increase my efficiency, after all what else can I do if I'm reinstalling on one machine and only have one keyboard, mouse and monitor? It would greatly decrease the turn around time and I could get the systems that are given to me to work on out faster. That would also give me more time to frag away, or to play with my new Prometeia. ;)