Many people here have probably heard of Action Replay, a.k.a tool of destruction. If you haven't, well to put it simply, it's a hardware used for cheating. I know you can get it for ds and wii but I'm not sure if it's been released for 3ds yet.
I know that action replays are old now, but there are still similar things out there.
My advice is, never get an action replay or anything similar to it. Seriously.
These are cartridges that slot into your consoles just like regular ds games and most people use them for hacking pokemon and animal crossing games. Obtaining shiny pokemon, rare candies, low level legendaries and editing the layout of animal crossing towns.
It completely ruins the fun of the game
Sure, It might start out being fun, but then you realize that you haven't actually achieved anything at all by beating the champion with your lv.100 6.IV shiny Arceus or by paying of the whole of your animal crossing mortgage with a hack.
I used to have an action replay (I was 9, and stupid) and after a few months, my animal crossing wild world town looked exactly like this:
which honestly is kinda fun at first, but then the novelty of it starts wearing down and you realise that you've wrecked your entire game. ._.
It can corrupt your game
For example, by using action replay hacks that allow you to catch other trainers's/ncp's pokemon, you can get a pokemon called a 'bad egg', if you get one, delete it straight away because when it hatches, it can permanently corrupt your game.;-;
I hope I've convinced some people to never use hacks :3