Well I guess it depends on the type of person your mother is. Mine would rather give me something I could use and would understand if i exchanged something. My mother-in-law is just the opposite. I don't mean to sound like I am wanting her to die, but when she does there will be a few things leaving my house soon after.
I don't like the presents my mum bought me and I feel like a brat if I tell her but I hate the thought that she spent money on things I'll never use.I feel so bad?
Edit: I told her and she seemed to be okay, she didn't spend as much money as I thought which is good but it doesn't sound like its returnable
I once gave my son (13 at the time) a Dremel tool for Christmas.
He was less than enthused.
A little later, I followed up with him. It turns out that he was looking at a tool next to the tool that I had bought and it was that tool that he really wanted to have.
Like you, he didn't want to hurt my feelings by telling me that what I bought was not what he wanted.
Personally, I think parents intend to give their children what they want if they can, and if things didn't work out that way, we parents want to know so we can correct the situation.
Tell your mom you really appreciate her effort in trying to give you something you want, but that your interest really lies in a different area.
That's certainly what I would want you to do if you were my child.