I have one of the Elecom trackballs and it's weird to get used to if you haven't used trackball but it's grand. I've had lots of wrist problems due to my hobbies of playing guitar and rampant self-love and this has definitely stopped a lot of the pain I had when using a mouse. There is a fast and a slow setting but I've never bothered with fast as I don't use it for gaming.

Here is one on US Amazon but you can get them easily over here. I even snagged a left-handed one but that was an import job from Japan.

Para qué no lo uso? Es lo más, tengo dos. Empecé a usar porque me jodía la muñeca y ahora lo uso para absolutamente todo. Incluso jugué DOTA, algún que otro FPS y todo...

El grandote con cable lo dejé en la máquina de escritorio y el de bola azul lo llevo en la mochila con la notebook.

También tengo ganas de comprarme éste