Lascannon
Unlike the Lasgun, the Las-cannon is a flashlight that may be considered bad ass.
The las-cannon is often placed as a phallic symbol on many Guardsmen Leman Russ, because they thought the battle cannon was not enough. Spas Mahreens often use them in their devastator squads, because they are simply better than their Guardsmen counterparts, and want to make sure that's clear. But like their Guard counterparts, they like to stick them on all the tanks they have, because they are Spas Mahreens, and they're cool like that.
Las-cannon are designed for anti-vehicle combat... sure... but really, they were what the Tau based their creation of the Rail Gun off of, just so they could say FUCK YOU to the Imperium and the Emprah's servants. Because a giant red deathbeam just isn't as cool as hyper magnetically accelerated shit flying from the shoulders or arms of a crisis suit on 'roids. For shame, GW, for shame....
Yes the Las-Cannon, for when a hellgun/hot shot lasgun(WTF GW, come on!) just isn't enough.