XM510 Multishot Grenade Launcher

The XM510 Multishot Grenade Launcher seems to be a semi-automatic grenade launcher used by the UNSC. In Halo Wars, an upgrade for the Warthog includes a marine equipped with an XM510 in the passenger seat to improve attack strength of the vehicle.

Trivia

 * The Halo Wars: Official Strategy Guide once mistakenly refers to the "XM511" as the "XM510" in a caption describing a weapon mounted on the MAAT-9 Wolverine. However, it's later correctly labeled as the "XM511" on the same page and elsewhere in the guide. Though one's mounted on a vehicle, it seems the two grenade launchers would appear and behave similarly.
 * The XM510 only appears in Halo Wars. It's most likely not included in the main Halo franchise due to its similarity in function to the Brute Shot.