In no particular order:
Anything by Team17 - those guys made BRILLIANT games which even by todays standards hold their own
The New Zealand Story
Chaos Engine
Cannon Fodder I & 2
Syndicate
Elite - Original BBC Micro Model B version (yes, mine still works!)
Honorable mention:
Hypersports on the C64 for the endless supply of broken joysticks I somehow managed to aquire trying to get as many somersaults in on the vaulting horse :-D
