I have read on xbit labs' 22" monitor roundup pt II http://www.xbitlabs.com/articles/monitors/display/22inc...
that the Asus VW222U is one of the the best gaming 22" monitors you can buy in terms of quick response time and low artifacts - certainly the one I'm eyeing up at the moment. The Samsung 2232 range are also supposed to be good for gaming and perhaps a little more stylish.
However it depends on what your priorities are, whether colour re-production, response time, look or price are more important to you.
The best advice is to read as many reviews as you can (ones that actually test several monitors properly) and then make your mind up from there.