Up here in New England, the climate is really harsh on full-sized trucks of this vintage. None of them seem to hold up. Here's what I've seen go wrong:
1999-06 GM trucks
-None of them have rocker panels or cab corners anymore
-Spring shackles/mounts also disintegrate
-So do the frames, actually
-DoD issues with trucks that have that "feature"
-Rear differential problems
-Even ones with issues sell for absurd money
2007-13 GM Trucks:
-Same as above, although the rust hasn't fully set in on some of them
1994-01 Dodge Ram:
-Everything rots, from bumper to bumper and everything in between
-All of them have paint issues, I've seen sheets of paint come off at highway speeds!
-Electrical problems
-Transmission problems
2002-09 Dodge Ram:
-0.0% still have their original rear wheel arches (it's unbelievable!!!), they are all rotted or creatively repaired
-Most have other rust issues as well
-4.7-equipped trucks have lots of engine problems, avoid those
-Interior design by Rubbermaid
Mod Motor Fords:
-Extended cab trucks are skeletal under the rear windows
-Some of them like to poop out spark plugs
-I see lots of them with bad transmissions for sale
-Timing chain issues
2000's Nissan Titans:
-Early trucks had brake problems, can be corrected with parts swapping
-5.6 makes good power and sounds cool, but is thirsty
1st Gen Tundras:
-Bad frames
-I believe the 4.7 V8 has a timing belt, and I'm sure that service is pricey
2nd Gen Tundras: (My dad has a 2008 SR5 4x4 with the 5.7L V8, so I'm very familiar with these)
-More bad frames
-Some trucks had issues with the cam phase actuators, should have been fixed by now
-Rear end axle bearings go prematurely, need special Toyota tools to repair
-Parts can be $$$$$
-My father's had an issue where the OEM replacement rear brake rotors made contact with the rear axle housing. Toyota's fix was to drop the rear axle and fit each side with an expensive kit at the tune of over $1000 to do the job; my solution was to slightly clearance it with a BFH for $0.00
The only trucks out of this group that I haven't seen rusted on a regular basis are the Nissan Titans. I've only seen one or two with rust issues, and those were beat to a pulp and had questionable body work that probably caused the rust.