Hello there, and welcome to PC! We hope you enjoy your stay! :3
I've played a few ROM hacks, but the one I would suggest the most is definitely Pokemon Sweet. The change to the type chart can be a little difficult to grasp, but the game is wonderfully unique, adorable and a blast to play through! Like Dragon said, there's also the ROM Hacking section, where you can find a lot of unique and fun ROM hacks to play and enjoy, so definitely pay a visit there!