The great thing about English is that you can just do that! In fact every word on the list started out that way. Of course there's situations where you shouldn't say fuckletoes out loud, like a children's birthday party, but it's perfectly appropriate bar slang, and of course in your head you're free to use it about that one kid as well.

I was leaning towards fuckletoes also, never heard dicksplash although it wouldn't be a surprise, but really any of them would generally be appropriate. You're supposed to get a little creative from time to time.

My favourite one that not so many people have heard is "that's rare as rocking horse shit".