Really an elevator would be a bad place to knock someone out or murder them. You would have to move the body as someone would easily find it there (easier said than done from an elevator). If you knock them out then you are only relying on if they remember that you hit them (since no witnesses). In addition there are cameras in almost all elevators these days, so it is unlikely to not have a witness. Bludgeoning is also messy and would be difficult to clean up after in an elevator.
I wouldn't want to be trapped in the elevator with someone who stinks at all, nevermind sticking their fingers in their ass. People in general piss me off though. Being trapped is bad enough by myself. Other than my friends, I hate almost everyone. Any child molestor, rapist or murderer would not be good to be trapped in an elevator with (as I hate them obviously). Really anyone that would be hard to tolerate for a long period of time, which would be most people.
As far as like to be trapped in an elevator with, hmm most really attractive women that I find interesting would work probably. I wouldn't mind so much with one of my friends either.