Casual:
* BF: This is the most common and widely understood abbreviation.
* Boyfriend: (Not slang, but still casual)
* SO: Stands for "significant other."
* Partner: Can be used for both romantic and platonic relationships.
* Man: This is a bit more informal and can sometimes be used playfully.
Affectionate:
* Babe: This is a sweet and affectionate term.
* Honey: This is another term of endearment.
* Sweetheart: This is a very affectionate term, often used in romantic relationships.
* Love: This is a very strong term of affection.
Humorous:
* Boo: This is a playful and cute term.
* Main squeeze: This is a fun and slightly old-fashioned term.
* Better half: This is a humorous and affectionate term.
* Leading man: This is a playful term for someone who is your significant other.
More informal:
* Dude: This is a casual term that can be used for a friend or boyfriend.
* Guy: This is a more general term that can be used for any male person.
The best slang term to use depends on the specific context and your relationship with the person you're talking about.