Whenever I get a gift card I prefer to simply empty it into my PayPal - Never wondered if PayPal themselves are okay with it so I'm asking now just in case.
I am also aware it takes a fee, but I really can't be bothered to enter a full gift card info anytime I buy a 5$ game.
You can't pay yourself, PayPal will shoot out an error message. And its also against TOS to cash out cards to yourself and ask others to help you do it.
