Any 4runner with the 3.0 v6 will blow head gaskets or just crap out in general. You're fine with any 96+ Runner v6 or any year 4cyl. I don't know what your needs are, but IMO the 4Runner is the only one with real off-road guts of those listed.

You'd be hard pressed to find a 4Runner 4wd with 100k for less than ten grand around here, so sounds like a decent deal to me.

:edit: Actually the Xterra is pretty decent off road as well, but pretty cheap-o on the interior. Also, be sure to keep up on the maintenance. My buddy's has recently snapped a t-belt and had a handful of other problems, but he kinda does the "fix it when it breaks" maintenance plan.

Cherokee is a good all-around truck, but will break if you do any serious off-roading without doing some upgrades first.

Also, a bit older than the other ones listed, but if you can find an fj80 Land Cruiser with low enough miles, those things are beasts. Kinda spendy on the gas front though.