Like BigSlam said, it really depends on how much you are going to use it as well as your budget. Here is the only one that I've had personal experience with:
http://www.northerntool.com/shop/tools/product_200451267_200451267
I've had this unit for close to 10 years now I would say, works great for the 1-2 deer a year that gets put through as well as an occasional hog. Might not be the fastest or most powerful on the market, but it has served me well for the money.
I'm considering this or the LEM line. I've always wanted a Kitchen Aid and this would be a good excuse for getting one.I use a meat grinder attachment for a kitchen aide stand mixer. It's worked perfect for many years.