Dell Ultrasharp U2711 27"
The Ultrasharp line of Dell monitors has long been among the best whre image quality is concerned. This is because they use an IPS display, which offers better color reproduction and better viewing angles than a TN display, the technology that most monitors use.
Ultrasharps have traditionally appealed mostly to digital artists and image editors, as it is able to produce a fuller spectrum of a color than a normal monitor, making the images on this monitor more realistic. These benefits also apply to games, however - there's really no other monitor on the market, besides other Dell Ultrasharps, that look as good. The resolution of 2560x1440 helps as well.
Traditionally, Ultrasharps have been questionable as gaming monitors due to high response times and ghosting issues. The U2711, however, has a response time of 6ms. Although not the quickest, response times have a floor below which any improvements are rather pointless. 6ms is more than adequate for gaming.
You'll find the only actual disadvantage is the price. You'll have to pay about $1000 for this monster. That's no small chunk of change!