Now, I say this because I'm having a look at setting up a new RPG campaign location and I want to do fantasy but I also love science fiction. This got me thinking about marrying up the two, a swords and sorcery in space mix-up, and one of the things that I was considering was dropping the whole 'magic is just psionics' angle and actually using proper magic as used in a fantasy setting. So instead of a bonus-giving magic sword you'd have a bonus-giving magic laser pistol. Runes etched into starship hulls create magical barriers, like shields. You could summon demons to fix your hovercar.
I'm in a fix, though - Warhammer 40K. It leans heavily on the fantasy side of things, so much in fact it sometimes seems they just swapped out swords for bolters, and so anything I do will be coloured by this highly successful game that's been out for more than twenty years.
So that means my work is cut out for me. If I do something similar then it'll be 'He's just copying WH40K!', and if I changed the aesthetic it'll be 'He's just copying WH40k and changed the design!', and if I try to do something different and try to keep that fantasy edge it'll be 'He's just copying WH40K and trying to do something different!'
Any way you look at it, I'm copying WH40K.