Spencer

Wonder Boy, My Knight

My Knight was simple he saved her from almost being killed, he was her knight in shining bulletproof armor

Wonder Boy was because he was a wonder to her.

Derek

Child

He acted like a complete and utter child around her so it was simple.

Hotch

Detective, Sherlock

Detective because well he was a detective. (I got nothing)

And Sherlock since he could figure her out in a second.