The British Army uses SA80s. Nice, relatively lightweight, and accurate, and guaranteed to work anywhere you go unless you leave Europe. At which point it melts, or clogs, or in some other way makes itself ridiculously useless.
The mark two version has recently been made, which removes most of the unreliablities, which actually makes it a damn fine weapon- if only we could make enough new ones. The SAS still refuse to use it, though, because of the loud safety catch.