There was a free to play fps called combat arms, it had a weapon loaning system where you rented guns for up to 90 days for in game currency (that you had to grind for) and obviously it was better than your default gun. Guns had premium variants that were straight upgrades. You could also pay to get grenade launchers and shit. It was so blatantly pay to win, it makes me cry thinking about it since it was a reasonably fun arcadey shooter.