PB 1400. Pure nostalgia: it was my first (and for many years only) PowerBook. I restored it from a cs/117 with a busted LCD to a c with a 466MHz G3, 60MB of RAM (RAMDoubled to 120), video out, modem and Ethernet, a new 4GB hard disk and a reconditioned battery. It still works great. Every release of Classilla is tested on it. And I love the keyboard and interchangeable cover plates. Plus, it is a very easy PowerBook to repair (as you can see).

If nostalgia didn't get in the way, I'd probably pick the 3400, but the 2300's form factor is so appealing ...