Tire liners are cheap and work well. I like 'em. I've seen guys make "redneck" liners simply by lining the inside of the tire with duct tape. Just thick enough to keep out goat heads.
I don't like slime tubes, they annoy me when topping off air, you have the sticky valve to deal with.
I don't like tubeless only because there's still chance of getting flat on a trail and then what do you do? Answer: get out a spare tube. Might as well just go tubed and carry spare anyways.