The wheels, the workhorse, the chariot or just plain and simple the bike.
My work horse in the period that I relearned about long distance cycling is a custom handbuilt Vittorio Rondoneur. Its a good old fashion steel frame which is pretty much indestructable. This bike is ideal for travel in third world countries that have something resembling roads. In my opinion its a bit on the heavy side for off road work, though its a great workhorse. My only complaint with Vittorio is that it was a crappy paint job, the paint started flaking off after a year (which they where happy to redo under warranty), but all the same from time to time bits of the paint still flake off( seams that it's not flexible enough).
Details for the bike spotters:
Frame : Chromoly steel lugged frame.
Wheels (28"): Rear 48 spoke tandem wheel -fairly indestructable. Front : shimano xt 36 spoke.
Racks : Front and rear are Vittorio self built racks. They are also fairly indestructable but rather on the heavy side.
Saddle: Brooks of course, a Flyer.
Pretty much the rest of the parts are shimano Deore which gives a good price/quality/weight ratio. Though most of the components are a little old fashion, i.e. cantilever breaks, square drive cranks, shifters etc. This was a delibrate choice to make it easier to find parts in less developed countries.
Tyres: most of my continental tyres have given alot of problems so from now on I'm going to try out Schwalbe tyres.
Lessons for my next bike? Lighter, compacter(easier for airtravel or in the back of my small car), and of course Rohloff.
Just before this trip I got my bike retrofitted with a Rohloff, it was a nice way to test out if a Rohloff is for me but a retrofit is always a comprimise (chain tensioner etc).