I think we can all agree that the coolest weapon ever is the lightsaber, right? OK then.
The second-coolest weapon ever, is the chainsword. It's the weapon that sealed he deal for me when it came to Warhammer 40,000.
Unlike the lightsaber, it doesn't really have a defensive quality - you're not going to be deflecting blaster shots with it, at least not deliberately. But it does have a visceral quality that 'sabers lack. You sweep a lightsaber past someone and they may not even realize their arm is off. A chainsword leaves no such confusion - they will know it, their nearby companions will know it, and everyone within a hundred feet will know it, thanks to the motorized ripping sound and the shower of gore that goes with it.
There are more powerful weapons in the 40K universe, but I think the humble chainsword is the coolest one of all.
I rarely post videos but this one pretty much covers everything that needs to be covered on the subject. Give it a second, it's worth it.