We are using an XLC chain breaker, and it has served us well. It's affordable and durable (only about ten bucks)
http://www.xlc-parts.com/produkte_de...4539,9358.html
For most chain tools you'll need a vice to clamp it because you need so much leverage.
Also Whatever you do don't buy the Bell one from walmart. It's cheap powdered steel that will snap quickly.