When I was a kid my father had a few mechanical pencils.

I found the endlessly frustrating. The erasers were always too small, and the lead broke routinely and got jammed in the mechanism. I avoided them.

Later I started to use mechanical drafting pencils at work for UI designs, and then, discovered Pentel mechanical pencils.

I still use mechanical pencils, particularly for drafting, and when I don't want to deal with sharpening a pencil. I've got some favorites though (KuruToga).

Lots of people love mechanical pencils, even the ubiquitous yellow plastic pencils from BIC.