UADetector is a library to identify over 190 different desktop and mobile browsers and 130 other User-Agents like feed readers, email clients and multimedia players. In addition, even more than 400 robots like BingBot, Googlebot or Yahoo Bot can be identified.
We got a case where people using IE on desktop with "Tablet PC 2.0" being detected as tablet. Please see the following two SO discussions for info: http://webmasters.stackexchange.com/questions/28569/why-would-an-ie8-in-a-desktop-has-a-tablet-pc-2-0-in-its-user-agent-string http://stackoverflow.com/questions/10213639/differentiate-ie7-browser-and-browser-in-ie7-compatibility-mode