I mostly use Monkeytype purely because of the customization. I’m a bit of a perfectionist, so I want the theme to be suited to whichever board I plug in.
Oh, and its UI is also great. I also love the keymap visualizer, it’s a great tool to learn other layouts and aside from that’s a neat addition. Feels much more refined than Typeracer.
Apart from that, when I want to have real fun, I go to https://jklm.fun/ and start a bombparty. It’s incredibly entertaining and actually requires creative thinking instead of just typing fast. Definitely recommend trying it out if you want something other than just typing some words.