I discovered this website this morning and it brings memories back from 97-98 when I was at school! We were using about 25 floppies to install this game on multiple workstations in the labs (the OS were reinstalled every nights).. until we found ipxcopy
Blood (the very first) has been the very best FPS I played because of the immersive atmosphere and the cool unique multiplayer features. I remember the booby traps! And the weapons were cool even way cooler than the moderm FPS...
I voted Blood because in many ways it is the best ever but i would like to mention Tron 2.0 also a Monolith game, as it's way up there with Blood for quality and fun