True, the major bots are probably CAT and Gunbot, the two being fairly similar and the latter only trading on Poloniex. You need to be warned though - these bots are not designed to automatically make profit for you and there is no bot that will consistently or accurately do so. These bots are mainly designed to assist your trading by:
1. Trading when you are asleep.
2. Carrying out your trading strategy with the appropriate coin of your choice.
You have to be experienced enough with trading to be able to use your own discretion in situations in which the bot will not be useful as the bot cannot handle every situation.
You also have to be prepared to have enough capital to make back your original investment of, in Gunbot's case for example 0.1 Bitcoin.
Thank you for the well written explanation. I dont think I would leave a strategy on for too long you need to change it as the market progresses or by hype which is human emotion. I do agree with leaving it over night because if you dont ypu might lose money selling or buying at a worse price because you were not there to check the market in that case a trading bot is a good option.