Well, the big two .68 pistols are the Tippmann TPX and the Tiberius 8.1
Assuming neither of those fit what you want, the BT SA-17 is really nice. If you get the rifle kit you can run it in pretty much any configuration you want.
That way you have the option to use 12g CO2's, remote line or directly attached bottle; hopper feed or 10 shot spring feed.
Unlike the other pistols, you don't need to spend money on magazines because you can use extremely cheap 10rd tubes.
The rifle kit also comes with some nice bore inserts and you can use whatever autococker threaded barrel you may already own.