To me the best SF weapon is Deckerd's pistol from Blade Runner. I don't know what it's supposed to be, it has two triggers and apparently throws exploding shells (one trigger for explosive, one for regular slugs?). Anyway it has a very cool, realistic and menacing bulky presence to it. I believe it was built from the receiver of a Steyr bolt-action rifle (which has a set trigger), with a wood grip, short barrel and various doo-dads added on.
In a similar vein, Star Wars had great weapons because they were made from real guns, so they had a very real-world weight and look to them, with spots of wear and so on. My favorite was always Solo's blaster, made from a Mauser C96 semi-automatic pistol. It was one of the first successful autoloading pistols, and looks pretty ungainly compared to the Browning designs that came after it, but with scope, muzzle cone &c. added on, its weird bulk is just about perfect as a SF blaster.
The TOS phaser II is just a classic, clean, almost art-deco design. It always caught my eye as a kid for having a short part out front and a long part in the back, the opposite of real and most fictional handguns. That just seemed really futuristic to me and I will always love that design.
I always liked the Logan's Run "blow torch" blasters as a kid. Did I read they ran on carbide gas? The sound was almost as cool as the muzzle blast. But the novel had a different Sandman weapon that always intrigued me. It was described as basically an updated Old West revolver, but each chamber held a different type of load, some lethal, some less so, and the cylinder could be rotated to fire a different projectile as the situation dictated. I can still remember their names, too: Ripper, nitro, vapor, tangler, needler, and homer. I don't remember what each one did, though, except for homer, which once fired could single out, track and kill a specific person.
--Justin
