quite a few... narrow it down a bit.. new / SH, springer / PCP, hi / mid / low end ?
Virtually all the theobens for example were offered .20 (gasram and Rapid range)
And a .20 barrel blank can be purchased and machinesd to fit a lot of others.. I made up a TX200 HC in .20 a while ago in fact (TX is a very easy gun to rebarrel)
HW springers are a sensible choice in .20, as easy to cal change if you don't like it.