Although the title of this mod - Black Ops - hints that it has to do with spy missions and other secretive stuff, you'd be wrong. This is Supreme Commander, remember - subtle means walking only one giant robot into your opponent's base, rather than five.
What this mod is really about then, is units. This makes it technically less of a mod and more of a unit-pack. But let's not get to picky about the semantics, because the fact remains that even if it is "only" a unit pack, it is a very popular one. It includes numerous units, some of which are insanely destructive and fun to use. In total, there are over forty new units added by the pack, including my personal favorites - user made dreadnoughts. Black Ops includes several, including the not-so-creatively named Bismark, a UEF battleship with massive cannons capable of raining down destruction from far, far away.
Besides the mega-units though, Black Ops also includes some utility players, like the Advanced Air Station, which is a sort of front-line resupply base for air units. Its not as exciting as massive battleships with a billion cannons, but its still useful.