Oh my Musharna is just so good. Whenever I build a team without her I always end up weak to Gurdurr and Sawk, no exceptions. Musharna is one of my favourite pivots into the tier, and she just has so many sets that work. SOme of my personal favourites are: CM Baton Pass, A pure support set with twave, the standard defensive Calm Mind, Offensive Trick Room, Specs all work really well. The one set that I think never gets enough attention is the Offensive Trick Room set. Musharna can easily set up Trick Room on half of the tier, and can easily sweep once her few counters are weakened. A set of Trick Room / Psychic / Signal Beam / HP Ground is my personal favourite, because it hits Absol, Skuntank, and Probopass super effectively. By using the appropriate coverage move the first time, and then setting up a sweep later Musharna can effectively lure in its counters and cripple them. Even if Musharna is killed right after setting up Trick Room you can easily send in a slow teammate and continue the rampage.
Another Musharna set I haven't seen in forever is the LO tank. Some of you might remember me hyping that set back in the Jynx meta, but I haven't seen it since. With 3 attacks and Moonlight, Musharna becomes the perfect hit and run Pokemon, she still has amazing bulk but now has much more immediate offensive presence as well (since with no SpA investment she is quite weak at first). I really want to try this set again, but the loss of bulk really sucks against CB Sawk, who would rip through the meta if not for Mushy.
BW2 really buffed Musharna, Signal Beam is a great move in NU, hitting Psychics and Darks in one move is just what Mush needed; back in BW1 I often found myself choosing between the two. Another huge buff Mushy got is Heal Bell. Heal Bell allows Musharna to support the team so much better than before; she can effectively run a mono-attacking set now, doing that in BW1 is suicide since Musharna is toxic bait to the extreme. Now if you don't have 3 super powered Pokemon to sac to the set, or a dark-type you flat out lose to the mono attacker. Its part of the reason every team I have has either Skuntank or Absol. So Musharna is a member of all of my teams, as well as a Musharna counter. She's that good.