Okay, so it's not quite the same as giving away a full game, but PlayStation Plus subscribers can currently nab the original Ghosts 'n Goblins for Capcom Arcade Stadium at no extra cost. Capcom Arcade Stadium itself is free to download on PS4 (and PS5 via backwards compatibility), but you need to cough up for the games and various other add-ons.
If you fancy some retro action, it could be worth the quick and painless download (Capcom Arcade Stadium weighs in at about 1.2GB). The quickest way to actually find Ghosts 'n Goblins on the PlayStation Store is hit it up in a manual search, since the Capcom Arcade Stadium page is a bit of a mess.
Think you'll give Ghosts 'n Goblins a shot? Recount your retro gaming sessions in the comments section below.