Leoric - I remember Defender OT Crown on the Amiga... brilliant game. Glorious graphics (at the time, anyway.)
I didn't realise we were going all the way back to the C64... anyone remember these:
Hades Nebula - perfectly balanced scrolling shoot 'em up.
RimRunner (I think) Something about giant lizards and ant people. Remember it being very very good.
Alien (C64 Version) - The game of the film - So scary I was afraid to play it on my own. (I was only a kid

)
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"Pinky, are you pondering what I'm pondering?"
"Uh, I think so Brain, but how are we gonna teach a goat to dance with flippers on? "