The fetish called forsitting on the cake is called the sugar icing.
A foot fetish.
An earlobe fetish.
Schediaphilia, is the word for that fetish. It is also know as toonophilia.
Fetish for small spaces is called claustrophilia.
There isn't really a special name, probably because it is not very common. It is simply called an elbow fetish.
Remembering that fetish means replacing normal object of sexual desire with the fetish object, I suggest you are seeing the gun as a phallic symbol.
Watersports
That is too normal to be called a fetish. Most men are intensely aroused by the female buttocks and anus.
That's so obscure I don't think there's even a name for it. I think it would just be called a report card fetish.
A piece of cake is simply called (and spelled) "a piece of cake." It may also be called "a serving of cake" or "a slice of cake."
There is a thing called a foot fetish,which is very common especially in male's. I don't have a foot fetish,and I know i'm not missing out on anything. A foot fetish is a sexual attraction to the feet. Usually the feet of a female. Girl's think of foot fetish boy's as "Creep's" or "Weirdo's" and I agree with them. Some has a fetish,and some have disgust. Which I have disgust.
They are called this because they are made lazily