It would be my Palm IIIx, but it's too durn big. The Palm V and it's ilk are the right size, but I know the screen would be destroyed in less than a month. What I really need is something the size of Compaq's Itsy with a protective cover over the screen.
Actually I'm thinking more along the lines of keeping the screen from being physically broken. I've slammed into more table corners than I like to remember and the flimsy cardboard cover that comes with the Palm V wouldn't help much for that. As far as scratching the screen, I did the stylus paper trick to "sand" the tip down and my screen still looks OK.
Sony Clie peg-s300. Picked it up at Office Depot about 6 months ago for $99 on clearance . Real small, great stock case, 8mb+8mb mem stick, built-in battery.. It's been serving me quite well. I just wish I could find another cradle for under $60.