With tubeless, you still need a way to add air to the tire because you could get a minor puncture that the sealant fixes, but you lose some air in the process as the sealant gets pushed out the puncture. And of course there's always a chance of an unfixable puncture or tear.
Here's what I carry: air pump, CO2, CO2 inflator, tire lever, tire plug tool (the Stan's mentioned above is good), and a tube.