Chances are you have. This program (written entirely in python) finds and retweets these types of tweets. It also automatically favorites the tweet if the word "favorite"/"fav" is in it, and/or it will follow the user if the word "follow" is in the tweet.
Here it is running. As you can see it found the word "follow" in a few tweets so it followed the user too. Maybe it's just me but I think that's pretty cool.
Modules and code
It's compatible with all versions of Python, and the only modules it requires are 'time' (built-in) and tweepy. You can install Tweepy with
pip install tweepy
The github repo for it is here.
Also -- you can get all the keys/tokens if you follow this guide.
I just looked at the last 20 things it has retweeted, and it retweeted 18 'good' tweets, and only 2 'bad' ones. A 'good' tweet is one that is a "Retweet for a chance to win"-type tweet, while a 'bad' tweet is a tweet that isn't a contest. I'd say that 90% valid retweets is pretty great.
You can check this for yourself; check out @beefbot9000
Feel free to do whatever with it, but if you get in trouble with Twitter you'd better not get me in trouble too.