Those defenses are just too low. I mean, even Fearow lasts longer. And the amount of weaknesses Sharpedo has doesn't help. But if you're good at predicting switches, using the right moves at the right time, and are just that little bit lucky, you may want to consider Sharpedo. At least you can use it as a Reversal / Flail counter. Must count for something.
This reflects the only real use of Sharpedo: abusing Rough Skin. It makes Sharpedo the best Reversal / Flail counter in the game, and every serious UU team should have at least one of these. When something hits 1 HP, Endure the hit. Rough Skin will kill them, and your Salac Berry will activate. Sweep what you can, though you will probably be met by your opponent's Quick Attacker or Mach Puncher.
Really, Sharpedo is mainly hit and run and should be played as such. The attacking versatility isn't bad, just hit stuff you can kill, and flee when you can't.
Whichever way you look at it, Choice Banded Sharpedo is not a great Pokémon. Perhaps if it were a little bit faster, it would be useful. But as it is, it's pretty much a slightly slower Fearow with slightly better moves and perhaps the worst defenses in the game... the special version is probably better because you can choose your move every turn, and STAB makes more of a difference than stats here.
Well, if you can predict a switch, you can score some use out of him. That attack power is still very high, and combined with Choice Band, you can have a killer on your hands. The likes of Manectric, Banette, Magmar, and maybe Fearow, Aggron and Jumpluff will fall in one hit if you select the right attack. Hydro Pump is there as it hits the folk with higher Defense, like Torkoal and especially Gligar.
Substitute actually isn't too bad on Sharpedo, if you predict a switch you can get the right move in later on, but Endure helps a lot to make Sharpedo stop Endure and Flail.
Max out Speed and Attack for the Choice Band set and Special Attack for the Endure set. The last EVs should go into Special Defense, since about the only things Sharpedo can survive are Surf and Ice Beam.
Checks and Counters
Any sort of sweeper puts this shark down for good. If Sharpedo doesn't kill, it will be killed. Watch out in particular for Fearow, Raticate, Raichu, Persian, Primeape, Tentacruel, Electabuzz, Jumpluff, Yanma (maybe), Sneasel, Linoone, Swellow and Manectric, all around the same speed as this shark, and all able to kill it with relative ease.