I know this is obvious, but Pokémon Go has an anti spoofing system built in. Most apps simply won't work and (I'm talking about Androids) rooted exploits will result in a ban.
Here's what happens when you get banned - 1. You can't get items from pokestops. 2. You can't catch Pokémon. Any Pokémon, irrespective of its CP, will run away after you throw a Pokeball. 3. You can't battle or claim a gym.
It's best that you don't attempt to cheat.
Source: I manually triggered a ban on my useless account to find out how they work.
Edit: The ban seems to be a softban, i.e. it is temporary (but we still don't know how many softbans can you get before a permanent ban). You'll probably need to wait an hour for it to go.
Edit 2: Please don't post cheats here and I'm not gonna respond to any questions regarding how to cheat.