What's your favourite Arduino model, past or present?

I think the Uno nailed it. Dead simple and ready to go out of the box, no fiddling with jumpers or whatever.

I'm not inclined to bother with the Due personally, but I think it's a good product to have in the lineup. All the weird form factors (the joystick for e.g.) and non-Atmel stuff is a dead-end IMO (but what do I know?)