I've been using my Palm T3 a lot over the last year. Useful for alarms/reminders on the go, and for contacts, as well as shopping lists (HandyShopper). Occasionally use calculator, units converter, memos, rarely anything else. One of the great things about it is I turn it on, and full power is immediately there. No waiting for the OS to boot up, anti-malware updates, etc, etc. Bliss after a corporate (or home) PC.
Most of the salesmen and managers where I used to work had BlackBerries, but I'm not sure how much it was because BBs are genuinely useful, or because BBs are this week's must-have accessory. But some of them did seem to use their BBs an awful lot for email.