Necros, Drd's (who CAN buy better rez thru CM), shammy's, Pally's (thru cm's only), and Clerics rez... Not sure if any Other classes do yet, But I do know those can.
The way rez works, is if you or someone in grp dies, you can be rez'd to reduce the death debt. Only within grp does rez work, meaning the person Has to be in the grp with the Rezzer (which is why not everyone can rez ppl calling out and asking for rez in towns; grps only consist of 4 and might be full) and there are two types of rezzing: On site (to stay where you are) or out of site (to go back to place of death). The class that Possess the Rez spell Does NOT have a choice: they don't get to stay in town if they must self-rez, they Rez back to point of death, and if died in a bad spot, must ask someone Else for a rez to stay and not risk bouncing back for double debt.
Hope this explains n helps ya =)