Depends on what you're looking for. Shantae and the Pirate's Curse is a great metroidvania platformer, Shadowrun Hongkong if you want to experience a cyberpunk+fantasy RPG, Rebel Galaxy for a space game with some trading and naval-style combat (ships don't move in up/down directions), Van Helsing for a diablo-like experience
I'm also seeing Hyperdimension Neptunia on the sale, though I have no clue if it's any good. I always get baffled by the amount of games in that series
KSP is still the best 'build an entire space program' sim, now that KSP2 has erm, failed to launch, or maybe suffered a RUD... and KSP 1 now has a decade of quite frankly astonishing expansive mods.
Try KSP Realism Overhaul and Principa if you want to up the difficulty a bit, lol.