The QBZ-95 bullpup infantry rifle from China, a.ka. Type 95 rifle, fires the proprietary 5.8x42mm round. Many small arms experts consider the ideal infantry/light machine gun caliber to be between 6mm and 6.5mm in diameter, and between 39mm and 45mm in length, making the new Chinese caliber very close to the ideal dual-purpose infantry round.
Click here for pics and info on the QBZ-95.