Well, this is some kind of miracle-thread for me: with the exeption of 'A scanner Darkly', which I haven't seen yet, I know - and for the most part - love every single one of the movies that were mentioned. This is truly a forum of likeminded folk :-)
Trying to come up with stuff that no one mentioned, but I have scanned the thread rather quickly, so I may have missed these:
- The Black Hole, riding on scifi wave created by Star Wars this Disney movie can be regarded as the ultimate derivative film. Visuals with a very Gerry Anderson (Thunderbirds, Space1999) feel, and a rehashed script from their own 20.000 leagues under the sea movie. But also: a very cool space-fortress ship, very effective sfx, nice casting and an ominous evil robot. I even loved the religious ending.
- Battle Beyond the Stars, talking about derivative, this Roger Corman production actually looks pretty big budget for once. It's The Magnificent Seven in Space, which was Seven Samurai in the west to begin with. Includes George 'Hannibal' Peppard als Space Cowboy, the Man From UNCLE and that guy that used to be John-Boy or something in one of those Idyllic Wild West (little house on the prairie?) series.
- Message from Space, Japanese attempt at making a Star Wars movie. Silliness that now had become quite commonplace, like sailing spaceships looking like 19th centrury clippers. The only movie I've seen that I don't actually own in some format or another, so I'm scetchy on the details. Didn't it revolve around some magical nuts? Weren't these things called Liabe-nuts?
Starcrash- David Hasselhof. Need we say any more? Okay then, Christopher Plummer as the emperor, and an evil count that actually does the "Mwhoehahaha"-evil laugh. A lot. And he lives in a space-castle-station that is shaped like a hand. When the hand is attacked it clenches like a fist. The movie was made after Star Wars, but looks like it was made in the sixties - at which time it would have impressed us all a lot more than it did in 1979 (or there abouts). Full of Harryhausen-type (not quite the quality) stop motion effects. Wonderful, wonderful sillyness.
I'll try to think of more...