DUDE!!! I do that, i made namecards (pressed them at the store) with my full name and phone number on it. When i like a girl i give her a card. I have always been complimented about them, they mostly find it funny amd refreshing. Its also easier to approach a girl like this and try to have contact. She can either accept it and call me or accept it and throw it in the garbage but idc because i won't know it ;)
This is actually more efficient since girls pretty often give fake numbers. Since guys are the ones that have no choice but to approach all the time, it's better to hand out your number and hope she calls.
I kinda like it. Guy chats it up with girl, offers is number instead (some girls aren't comfortable exchanging numbers even if they do like you) and leaves it up to her (it's almost always up to the woman how far things go). If he hears from her then great, if not then the guy knows he didn't leave a good enough impression on her and he can move on. No more meaningless text with one party not really being into the other.