First dude, the best shock off all times, according to people who tryed it, is the Canecreek Double Barrel. But let's see the others shocks.
First, the DHX 5,0 Air. This shock is lighter than it's brother, the coil version. Easy to adjust via an high pressure pump (Schrader valve). It become sticky and less plush with time as all air shocks and forks. When it is, it needs a rebuild. Remember that air shocks are linear so smooths but bottoming more easily.
Adjustments : Rebound, Air pressure(preload), bottom-out, Propedal (low speed compression), boost-valve(tuning range).
The DHX 5,0 Coil now. I've been trying this shock for few weeks and I can say it that it is awesome. It is a bit heavier than the air version but this can be partially solved with the use of a titanium spring. The feeling is more progressive due to the coil.
Adjustments : Rebound, preload via coil spring, bottom-out, Propedal (low speed compression), boost-valve(tuning range).
Marzocchi Rocco. I've heard good things about it. It seems to be even plusher than the DHX and let's say that little fox was the benchmark for so many years. I've been trying the HSCV damping on my 66 fork for two years and it works great, using always all the travel without bottoming. Oh I forgot, it is user servicable!
Adjustments : rebound via coil spring, preload, low/high speed compression adjustments.
Manitou 6 ways is not a good choice. Otherwise, the Revox seems to be a nice shock. I really don't know. In fact, it is a smoother 6 ways by the use of a new damping (Intrinsic).
Adjustments : High/Low speed compression adjustments, air platform pressure via schrader valve, rebound, preload and bottom out adjustements can also be found on this shock.