I don't want the gift that my boyfriend bought me for our anniversary.
Why don't you want the gift your boyfriend bought you for your anniversary?
It's not something I really want, he never buys me gifts that I like.
I know you don't like the gifts he buys for you, but he means well. You should always accept a gift that someone bought for you. You could try to make suggestions of things you like to try to improve his gift selection.
Nah, I'm just going to throw a tantrum because he's not doing what I want.
That's a childish way to get what you want. Your boyfriend will see this and would not want to get you anything in the future.