Only two at the cinema (although many many times watching DVD's).
Gremlins 2 (for the last 20 mins or so), and Star Trek 3 - The Search For Spock (for the entire film).
To be fair to Star Trek, the cinema was having an all-nighter, showing the first 6 films (the 6th had only just been released), so I wasn't the only person who fell asleep. At least I picked one of the worst films ever to do it in.