When I was playing dying light with friend we discovered that every timw you go to sleep and wake up air drop will appear, if you don’t know air drops are pretty rare and if you collext them and deliver to one guy you will recieve lots of xp, we used that multiple times to unlock grapling hook very early. Air drops also gave lots of medicine which was hard to get in early game and that very helped us
In Guild Wars 2, you can convert in-game gold to premium gems and vice versa. I discovered you could convert a really specific amount of gold, something like a couple hundred, to a massively inflated amount of gems, like 10x the conversion rate. You could then convert some of those gems back to gold and cycle this for infinite gold and gems.
I didn’t wanna get banned, so I did enough to confirm it worked and submitted a ticket - never heard anything from them, but a couple weeks later it was fixed.