Multilaser

Multilasers are the standard armament of the Imperial Guard Chimera transport. They're basically a Lasgun modded with multiple barrels and bulked up to the point where it's firing a fairly powerful beam with a high firing rate. It's a pretty good weapon against just about anything that isn't heavy armor (especially infantry with shitty armor, light vehicles, and skimmers), though like most Imperial Guard anti-infantry weapons, the Multilaser's armor-piercing capability is pretty weak. It's still a good enough weapon to threaten squads with, which is a big reason that it's the weapon of choice for Imperial Guard APCs, Walkers, and some Valkyrie assault craft. But mostly Chimeras, due to being an excellent suppression weapon to cover dismounted troop squads with (not that the game has mechanics for suppression except from sniper fire.) In the mediocre game Fire Warrior, they are also occasionally used as weapon emplacements. To help you visualize what a multilaser is like, we point you to the gatling laser of Fallout fame. The weapons are more or less identical (except that the Multilaser is still slightly less powerful since it can't vaporize robots in a single shot.)

Multilasers and C.S.Goto

The Multilaser is, by and large, unique to the Imperial Guard; sadly this has not stopped the violator of paper and ink known as C.S.Goto from completely disregarding everything remotely resembling canon and cramming them onto absolutely everything due to his raging hardon for the damned things. As of so far, Goto has managed to rape canon in more than a dozen ways using this weapon alone, including giving them to Space Marines and mounting them on Land Raiders (and not out of desperation either, this was the chapter's normal crusade-ready loadout).