Swords Without Master is such fertile ground for hacking! I've heard there's a pretty good Star Wars hack out there but I'd love to see more stuff coming out for it.
I'd also love to see someone hack Trouble for Hire by Nathan Paoletta. It divides traditional GM and setting tasks between players in a really cool, fluid way.
Not to self promote too hard but I published a hack of The Quiet Year this past year! The Summer Greening: A Blackwood Tale is a game about a society of bold rangers trying to hold themselves together as their forest territory grows weirder and weirder through the seasons. It's not a super innovative hack but it was fun to tweak the kind of story told through the card draws.