UT99 will be on the shopping list if I had to stay on a little island.
By modern standards it looks a bit dated, but so do Dune 2 and X-Wing. It's the gameplay that I find to be unbeatable by any other FPS game. Loads of user made maps and mods to choose from. Some mutators are really sick. My favourites have always been the Strangelove Redeemer and the Crotch Shot ones. Yeah the last one sounds nasty and it is, but it's great fun and a nice addition to the gore which the game already has.
The follow ups of this game are, apart from the cartoony UT2004, not that great. UT2003 could have been skipped, and UT3 doesn't really give me the UT99 feeling either. I've played this game from day 1, and it will remain on my hard disk for years to come.