Useless Power-ups
I don't know, Towards the end of SA2 where you had to fight those Fake Chaoses I found the Light Speed Attack a fairly useful method for taking them out.

And The Magic hand was most definitely a -very- useless power-up. It was more along the lines of a gimmicky kind of thing.
Despite the fact that it was useless, I still kind of enjoyed bowling with enemies in little glass balls.