it was fun to own shit your friends couldn't own ;O;
thats the most fun i had from theese devices..
hey
@Psionic Roshambo got plenty of gamesharks he could talk about his early days to sell pokemons to friends (i think that was it?)
Oh yeah I used to download the saves with the early GS that could only dump saves and edit them on a PC then re upload them all hacked up. Then use the WiFi trade thing on the original DS and people would pay like 5 bucks for those things... Then come back and buy more... turns out he was selling them at school for 10 bucks lol
But before that my earliest hacking experience was with programs called nibblers on the old 8 bit computers that would let you copy disks and bypass copy protections

Running into new sector/track based protection schemes on the latest Apple IIe releases was always cool and trying to figure out why the copies would fail.... Fun times
Edit: I still have that very same GameShark and the weird cable it came with, is some sort of custom super small USB type plug on the cart end and USB on the other end.
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On the original post, I have most of these devices, I collect them

easier to name off the ones I don't have (at least that I am aware of)
Missing the C64 Action Replay and the NES Game Genie. The Genesis and Saturn ones... I have PS1, PS2, GB, GBA, SNES, N64, Dreamcast, some of these I have multiple versions like both versions for the N64 and the PS1 and PS2 I have a few different versions and some of them with collector tins and stuff, the Dreamcast I have the one with the cool memory card dongle thing. I know I have more than these but I can't remember them off hand... lol I have a couple of versions on the GBA and the DS also.
Some of these really where a metric ton of fun, owning a SNES and the Game Genie and Street Fighter 2 Turbo back in the day was 10 out of 10 worth it... The codes for that game where insane like super speeds, air moves, and some friends some beers and you didn't need other games. lol
Edit:
I never owned a gameshark growing up - but my best mate had one. I was always so impressed by the thing. Especially because he had Mew and Celebi.
It wasn't years later til I realized cheating in a game ruins the fun.
Still fun to use the levitate code in Ocarina of time and Majora's mask to this day tho.
They are like any tool, you can use them to suck the fun right out of games or you can use them at times to make shitty games playable or add features to games that where never intended making the games last longer.
I used to like to stick random codes in just to see if anything would happen (99.9999% of the time nothing or the game would crash.) the rest usually involved some sort of corruption lol