I've been messing around with Magnezone. It has a lot going on, and it's difficult to set up, but if you can set it up, it's tons of fun. I use two Electric SF Magnezones, one DP Magnezone, and the Lv. X (I don't have a Metal SF Magnezone handy or I would try that out). I focused on throwing an Expert Belt on SF Magnezone, hitting with Gyro Ball for 80, and switching to a Spritomb or a Metal Magnezone loaded with Special Metal energy. You take advantage of the X and DP Magnezone to move around energies each turn to move SF Mags back into active and continue the hit-and-run strategy. If you need some extra damage or paralysis for breathing room (not taking the bajillion ways to maneuver around paralysis into account), you can use Cyber Shock instead, since it's easy to recover energy.
Staples:
Spirtomb PA
Gets some extra usefulness by adding a trainer lock to the hit-and-run strategy and also gets free retreat with DP Mags in play.
Claydol GE
Self-Explanatory
Possible support:
Palkia Lv. X
Use its power to pull out potential threats before they set up or techs for easy KOs. Lv. X and DP Magnezone let you get SF Magnezone back into the active spot afterward. Pretty much required to maximize SF Magnezone's effectiveness.
Electivire Lv. X
Slows down SPs by making attaching Energy Gains risky, and SW Electivire can pull energy out of the discard if you're relying on Cyber Shock for damage.
Manetric PL/Bench Shield
Flygon Lv. X will destroy you with the quickness if you run all of the previously mentioned Xes without some way to protect your bench.
Nidoqueen/Blissey Prime
It boils down to preference. The hit-and-run strategy is going to build up some damage on a lot of your Pokemon over time, so you can use Nidoqueen to heal as you rotate through your Pokemon (not to mention in makes Electric SF Magnezone's power's damaging effect a non-issue). Blissey is an option because of Magnezone Lv. X's power, which lets you avoid the discard, but you'll probably need a few Super Scoop Ups, too.
Magnezone pretty much loses automatically to any deck with DP Dusknoir because of how much bench space it requires, so keep that in mind and make it your top priority to KO any Duskull in play.