I'm putting my vote in for Dungeons the Dragoning: 40,000 7th Edition.

While it's high-tech in the vein of warhammer 40k, medieval type weapons are just as, if not more at times, useful. There are sword schools and gun kata alongside the magic schools, allowing you to create elaborate and powerful special abilities for melee and ranged weapons respectively, made even stronger by the robust stunting rules giving your players bonuses for trying off the wall and insane ideas with the environment. There are rules for ship combat, land combat, vehicle combat, aerial combat, etc. All of the spaceships are built from the ground up allowing you to customize it to your liking with many different ship classes ranging from a tiny corvette to a massive flagship battleship, all of which you're able to buy with enough investment.

There is a casting system with magic schools based on wh40k psionics with powerful effects if you miscast. However, miscasting doesn't necessarily mean that you didn't cast the spell, it just means that something else happens in addition to the effects of the spell if you hit the target number for the spell. If you don't hit the target number, the spell fizzles but you still might have to deal with the extra effects from the casting process anyways.

Cybernetics are part of the base game and one of the exaltations is the promethian which is basically a robocop/GitS/DC Cyborg type character. Oh and speaking of which there's exaltations, special powers that make you a cut above the rest from the very first level like vampires, werewolves, cyborgs, kryptonians, demon-posessed, "special otherkin", and far more. Many races to choose from with the formatting easy to get a hold of and make more content for. Even better, since the entire system is a cobbled together frankenstein formed from the corpses of like 7-10 other rpgs and animated with the unholy spark of a dare set to be released on april fool's day, it's completely homebrew friendly and entirely free. It's also one of the best games I've ever played.