No paintball gun is ever truly obsolete, since as long as they can shoot a ball someone out there will be using one to play.
The venerable 98 is still being made (or they made so many that supply is still plentiful) and still available new, with plenty of support. Many of Tippmann's newer models are basically just 98's in a different shell.
They gun that Tippmann currently markets as their rental gun is the FT-12.
Basically a 98 internally, but with the grip moved forward (for smaller renters), and the top flips open (FT stands for Flip Top) for easy cleaning.