Many of the works of H.P. Lovecraft approach the ideas and themes of raygun fantasy, though the lack of human space travel tends to push it away. Still, the concept that what we know as "magic" could well be alien science touches on the merging of the material and the psychological that characterizes, to some extent, much raygun fantasy. It is, perhaps, not surprising then that we find later Lovecraftian authors (such as Toren Atkinson, whose roleplaying game Spaceship Zero is one I'll be dealing with as I discuss raygun fantasy RPGs) finding their way into the fold.
It's been suggested that Space 1999 would fit into the concept, though it has been a long while since I have seen the show so I can't commit to that, nor comment further.
Similarly Jack Vance's "Five Demon Princes" tales. I haven't read them, so can't comment on the idea.
Galaxy's first-issue manifesto to heart. Heinlein was also an occasional practitioner of the closely related, but different, subgenre of science fantasy, notably in "Magic, Inc." and Glory Road.
While I'm at it, I am going to start listing roleplaying products that fit into the idea of raygun fantasy, or at least scientifiction, but without comment (or at least not much). I'll avoid more science fantasy entries such as Spelljammer or Empire of the Petal Throne, as well as edge cases like Gamma World, Metamorphosis Alpha, and Mutant Future:
Anomalous Subsurface Environment (depending to some extent on how it's run)
Burning Sands: Jihad (supplement for The Burning Wheel; a Dune knockoff)
Carcosa (tends toward planetary romance)
Dark Space (supplement for Spacemaster/Rolemaster)
Dune: Chronicles of the Imperium (Last Unicorn Games's last gasp, released by WotC in a limited edition after acquiring them)
Flash Gordon and the Warriors of Mongo (hardly an RPG by today's standards)
GURPS (3E) Lensman
GURPS (3E) Mars ("Dying Mars" chapter)
GURPS (3E) Planet Krishna
GURPS (4E) Tales of the Solar Patrol
High Adventure Cliffhangers: Buck Rogers Adventure Game
Hulks & Horrors
Lords of Creation (at least some realities)
Machinations of the Space Princess
Prime Directive (or its conversions to other systems, such as GURPS Prime Directive; while the Starfleet Universe of ADB tends to try to avoid raygun fantasy ideas, at least when they interfere with the militaristic approach of the setting, going so far as to have the Organians simply leave without explanation, there are some indications that raygun fantasy remains involved where it can provide a tactical exercise, such as the Loriyill of the Omega Sector)
Savage Swords of Athanor
Star Trek (two different companies to date, FASA and Last Unicorn Games, plus fan projects; limited to Original Series and Animated Series eras, and possibly the original cast movies)
Star Wars (three different companies to date with official games, plus fan projects like Star Wars Galactic Adventures)
Stars Without Number
Starships & Spacemen (to some extent, anyway, as a Star Trek knockoff)
Tales of the Space Princess
Under the Broken Moon (Thundarr RPG)
Under the Dying Sun (unfinished project, sadly)
Under the Moons of Zoon
Warriors of the Red Planet
The World of Thundarr the Barbarian (supplement for Mutant Future)
I look forward to hearing other suggestions. I'll discuss the RPGs in more detail as time goes on.