On my Omanyte project that will start at some near point in the future, whose male parent is a quint flawless Shellder, with Icicle Spear, Rapid Spin, Screech, and Barrier (which will be evolved into a Cloysters with Spikes and Toxic Spikes), and Stealth Rock put onto the best Omanyte after layers upon layers of incest...
So, Spikes, Toxic Spikes, and Stealth Rock will be on the Omastar so far. Gonna need a good fourth move to add to the project. Can't use Knock Off, or any Emerald moves. Aurora Beam and Bubblebeam are foolish, Haze would require me to breed it from a Quagsire, to an Omanyte, but then miss out on Spikes and Toxic Spikes (and ignore those lovely parents I have for a while), Wring Out just seems like a bad idea, Supersonic is eh, Slam is even less useful, and Rock Slide's a TM as well.
So, Protect? Ice Beam or Surf to avoid Taunt disabling? The analysis doesn't go into using all three moves on a set, probably because it leaves the Pokemon so horribly vulnerable. I just want the fourth move to be available to those who might want it, and this movelist may or may not represent what people will use for their final movelist.