Fashion, Beauty, Art, Music (but not the Top40 garbage on the radio), retro gaming (got a lot of these), card games, board games, dice games, RPGs with or without a screen (meaning that tabletop RPGs are just as fun), LGBT - related gaming and art, among others, in no particular order (if any at all)...
I like Emerald's Skill Trees script, it definitely has a good amount of features and is somewhat easily customizable, but I keep wondering if there's one that's even more modular and less resource heavy.