1. Business cards. Make you feel all professional and sophisticated, when you hand out one. Moreover it is much more handy than writing down your contact info on a random strip of paper.
2. Kuksa (aka kåsa, aka guksi, aka magic cup). Not only it makes any drink taste great, it also draws attention everywhere I go. Mongolians were particularly fascinated by kuksa.
3. Nexus One. Not much use as a phone when abroad, but music player, wi-fi, Lonely Planet in PDF, Angry Birds, offline maps (yet to figure that out, though) and myriads of other things make it a perfect travel companion. Only if battery lasted a little bit longer.

Other notable things:

Buff. Doubles as a hat, a respirator, a scarf and an eye-cover.
Silk linen bag. Keeps you warm when cold, keeps you cool when hot, takes little space and does not weight pretty much at all. Plus it allows you to sleep in filthy hostels and guesthouses without worrying about bed sheets.
A piece of rope. Makes wonders for drying your laundry.