There was a glitch where people could sell unlimited times the same car in GTA Online and basically make huge amount of money per day. They were "selling" an expensive vehicle for more than 2 millions each time and quickly became rich. Anyway, not sure if Rockstar has patched it, but as I know them they surely did as they only fix money glitches -- not the big gameplay bugs. By the way, never tried that money glitch.
There is this football manager games that I always play, it is known as Top Eleven football manager. There was a glitch in the past that enables one to train the players using friendly games. That glitch made it fun as I was able to train my boys to superstar level within a short period of time. The game developers discovered it and put a stop to it and it still hurts.
I remember the game glitch where some of the enemies could not see me in the serious sam game. I think that glitch saved me a lot of time and managed to walk a distance before AI detected me. It was definitely fun to see that glitch.
I've had a fun glitch before on PUBG where me and my friends where mucking around whilst doing some looting and I thought it would be fun to grab the nearby snowmobile and reverse it into the house where he was looting. That bit went fine although I'm not sure it was meant to go in there in the first place as it got a bit hard to mash it through the door. I managed to get it halfway in before I thought stuff it and just for a giggle, decided to close the door on it. What happened next was a combination of a flailing snowmobile suddenly exploding and wiping out two of my squad. Luckily we all laughed haha.
Back in the day when I used to play Ocarina of Time, there were a bunch of glitches I used to try and I really liked, such as exiting the fishing pond with the fishing rod. But that was just the beginning weird things happened when you used Link while holding said rod. Like you could use items while riding Epona.
Then there was that one to overwrite bottles in other items of the menu, haha. It was all fun and games until you accidentally saved your file out of habit and couldn't recover key items you needed.
Another popular glitch is "Infinite Sword" Link where you could bug the game into making the sword cut anything it touches no matter where you're pointing it.
There is another one I remember but I can't remember the full effect I think it was just to muck around. I remember we'd use Nayru's love and then use a warp son, and I think your magic would be consumed but you wouldn't have the protection, and the blue diamond wouldn't be around Link but the effect of it being active would still be sounding clear. Hahaha.
Gen 1 and Gen 2 of Pokemon are full of amazing, yet hilarious glitches. My favorite glitch is ACE (Arbitrary Code Execution) using glitched items. You can literally manipulate the game's code and add your own code. Here's a explanation, the games are written in gameboy z80 assembler. Each item is represented as a hex value, and each hex value represents assembly code. Tossing a certain value of an item will help manipulate hex values, and using a glitch item executes your code. From there you can obtain every Pokemon in the game, or for more advance code manipulate Pikachu's PCM cry to another PCM clip, and change the text for a more simple example.