Revolver is not just a potty-mouthed rock and roll magazine, a mediocre movie by Guy Ritchie, or a legitimate means of settling arguments in Texas (actual successful murder defense: "he needed killin',") it's also a tricksy carabiner design from DMM.
The 1.6oz Revolver carabiner has a burly little pulley built into the frame. It's definitely smooth, if slightly less efficient than a normal (larger) pulley. Used on the rope end of a quickdraw it reduces rope drag, but I got two to carry as part of my crevasse rescue rig. If my partner goes in the slot I (1) get his credit card number, (2) place an anchor and clip in a Mini-Traxion to a VaporLock (after sliding one of my Texas system prussiks above and one below the master point) and let it take the weight, (3) clip in one Revolver to each prussik and (4) clip the end of the rope into the master. Presto, a ZxC haul system.
All this requires two prussiks, two Revolvers, a Mini-Traxion, two Yates cable pickets and two Black Diamond Express ice screws (for snow and ice conditions respectively), a VaporLock (master point) and a CAMP Nano 23 (end of the rope) for a total of 3.5 pounds of gear. A locking version of the Revolver should be available "real soon now."