1. Holding parts from the other vises that you'll end up buying and restoring if you keep reading this thread
We never had one in the family when I grew up either, so it took me awhile to get one and start using it. Here's some random tasks that they've helped me with: cutting wood strips, changing CV joints, changing bicycle tubes, bending motorcycle skid plate, welding, pressing dents out of the bottom edges of a metal cabinet, wire wheeling rusty metal, cutting pipes, fixing legs on a chair...
If you don't have one yet, get a quality clamp on vise. It's easy to attach and move around and you don't have to drill any holes or over think exactly where you want it. Once you have it clamped onto a bench or tabletop you'll probably find uses for it.