Runescape. Stopped playing it 5 years ago or so, but still had mates who stuck with it so I wrote a bunch of autoers. The UI has changed so much since then one are likely to work, and I don't keep any updated since I know of no one who'd use them.
Back then, however, I was quite proud of all the anti-detection gizmos I put in, right down to moving the mouse realisticly (As a future-proofing method, I don't believe there was anything in-game tod etect computerized mosue movements) and inserting typing mistakes. Those were the days
Makes me curious how much is put into Abrosia for the same sort of thing - it seems successful enough, but I'm fairly certain it does some stuff that makes it glaringly obvious the account is autobuying if someone at TNT put even a small amount of thought into it.