Uh, I'm pretty sure parting shot doesn't do any damage. In the video, as soon as the move was used, it lowered stats without showing any signs of the opposing Pokemon flinching. Usually, if a move does any damage, the damage comes before the stat lowering, so unless they're changing that mechanic, it's safe to assume that parting shot doesn't do any damage. I think it's a fairly balanced move that promotes stall. Parting shot would kill offensive teams if used right.
Looking at the video, it does seem likely that it doesn't do any damage, which leaves me a little less worried about how overpowered it sounds. But if it doesn't do any damage, then what would happen if a Pokemon with Prankster learned it? I'd imagine that it could be incredibly useful, perhaps even to the point of being overpowered. If any currently existing Prankster were to get Parting Shot, I think Sableye would be the most likely suspect (or Riolu, if LC is taken into account.) Fighting seems to be the most likely type for this move, and most other Pranksters are flying, so it seems unlikely that they'd get it. Besides, this kind of trickery seems to be right up Sableye's alley, and could be a useful tool to somehow make him even more annoying that he already is.
But even without Prankster, Parting shot could be a threat. It's hard to know what kind of distribution it will get, but I think that Mienshao would be a perfect fit for this move. If it is indeed fighting, he stands a decent chance to get it, and it fits well with his hit-and-run strategy. In the current metagame, he commonly runs U-turn, abusing his high speed and Regenerator to maintain momentum while maintaining his own health. With this new toy, he might be able to disrupt opponents even more effectively.
The other move that caught my eye was Parabolic Charge, an electric type clone of Drain Punch. Drain punch is mostly found on slow, bulky Pokemon like Conkeldurr, in conjunction with Bulk Up. Electric types usually call to mind fast, frail special attackers, so it seems unlikely that this move will see much competitive use. The best hope for this move, in my opinion, would be Eelektross, who could run a set with Coil and Parabolic Charge, similar to Conkeldurr's Bulk Up and Drain Punch. Unfortunately, it is held back by its movepool, which is incapable of capitalizing on Coil's accuracy boost, as well as its lackluster stats. Free healing is a notable step up from Wild Charge's recoil, but I doubt it will let him take OU by storm. Electivire is probably the only other potential user worth mentioning, as he is the only Electric-type with a usable Attack stat outside of ubers and NU.
Of course, as with everything else to be said about X and Y, this is really just baseless speculation. Until the games are released, and a proper metagame is established, nothing can be said for sure.
