Claws, Shockwave.
It had good range for a scrapper, decent damage when slotted properly, and not to mention a fairly good cone radius for hitting everything in front of you, plus it recharged pretty swiftly considering how good of a power it was overall. Besides, knocking a dozen enemies on their butts at a time always made me smile.
Only issues with it was when I got the occasional PuG where someone complained about knockback all the time... I'm knocking them on their butt so they can't attack us until they get back up, giving our team greater survivability when the team has no controller or the controller we do have isn't doing their job properly, and they're complaining? Sheesh...
Speaking of which, I swear there were times when my scrapper felt as much like a controller as he did a scrapper, particularly when I would occasionally respec to have Darkness Mastery(Something about Tenebrous Tentacles always drew me back to the set...)... Shockwave to knock 'em down, Tenebrous Tentacles to keep 'em rooted, Petrifying Gaze to hold a particularly nasty mob (Such as a Sapper or Quantum) plus the IO in Focus that had a chance to hold enemies, not to mention it's knockdown and the fact that Focus recharged ridiculously fast for as powerful as it was.... Heck, with Hasten up, there were times I juggled enemies to death and they never got off a single attack on me... Still, I think Shockwave was the key opening attack to any attack chain I put together with all the various powers I had.