Probably my two most used generators are Fantasynamegenerators.com for names for my stories and games, and Dinopass.com for human readable (but still secure) passwords. Back when I made websites for commercial customers, I used to use credit card generators, since I had to send dummy data through purchase forms to make sure everything worked correctly.
I'm not sure what else I'd want in terms of tools that aren't available right now. For a while I've been wanting an app that ONLY does palette building and manipulation, since I work with palettes a lot when I'm making pixel art. It always seems like the palette saving/editing tools within art programs are an afterthought and aren't really robust enough for me.