I'm astonished by how far those aim trainer tools go haha, and how popular they are. I discovered Aimlabs[1] recently, which seems like the most popular one, and it has 6 000 people playing right now.

For us keyboard geeks, there is monkeytype: https://monkeytype.com/

[1] https://store.steampowered.com/app/714010/Aimlabs/