I was working at a mid size software company as an intern. Initially I wasn't going to get paid as it was organised through Uni. But then after some discussions with HR, they had agreed to pay me (sweet!). After 6 months of interning (and being paid) I talked with the CEO and he offered me a full time job after Uni. "We'll pay you now" he joked. I told him that the company was already paying me and I was very happy. "Well that's a mistake. You'll have to pay that back" So he wrote up a contract where I would work for them, but my salary would be reduced $15k over the year as "payment".

On that day I was pretty pissed, and I got an email from my current employer saying they were looking for grads. I applied and got the job! I ran away from my old job. I sent one email asking them if they wanted the money (as I wanted to be honest), but they didn't respond. I didn't try again and have kept the money, and am very happy at my current job!