Hmmm...besides Arena and Coliseum (which I like, but could be percieved negatively as a place of galaditoral combat between superbeings by 'the press')...
Penetrating Attack, IMO, should cost more; it's double indemnity against Protection and Saves. If I want to thwart it, I have to buy an Extra on a power that MIGHT be affected by it, but those using it only have to pay for it as a power stunt. Even if I buy Impervious, my saves are still affected by Penetrating Attack - there's no way to stop it from hurting my Damage Save. That alone should make it an Extra, IMO - its ability to affect any power that offers Protection to a character definitely should make it an extra; if I have to spend X points to combat it, the person using it should have to spend X points to benefit from it.
My pecking order comments, of course, are in jest...
Uhh, its only effect is to treat protection as if it was Amazing Save instead. There are a couple feats that negate a single power, true sight, see invisible, etc. As far as impervious, impervious cancels out a number of penetrating attacks equal to its rank, so if you simply bought it as a power stunt it would cancel the penetrating attack just fine. Penetrting attack has been altered by errata quite a bit over time, but simply forcing a save roll instead of allowing someone to automatically save is not out of line for a feat.