For something you drive quite a bit on road, I would look at the Truetrak or an ARB. The lunch box lockers are great off-road but have a tendency to make on road driving in slick conditions tricky.
A g80 is great but has a bad rep for exploding because people treat them like your standard pos-unit. It takes slow, light, steady throttle to get them locked up without damaging them but they did work quite well most of the time. They will not replace a locker if you are wanting traction with one tire in the air though.