Blaster type pistols, which are more probable than ray guns, with their compact, bullet-like bursts of energy output are also a very cool thing to envision. The image at the top is one of my purchased and manufactured prop replicas of pistols from various sci-fi features - This one is a realistic replica of the blaster which Bruce Willis carried as the lead character, Korbin Dallas, in the entertaining 1997 film about the future, The Fifth Element. It's got clean detailing and flashing diodes like the actual film prop. When held, it has the feel, heft and balance of a real firearm - That is obviously a VERY important quality I appreciate in a prop fantasy gun.
The next image is of a blaster I put together from a modified Nerf toy, which I thought looked pretty neat to begin with. It's a very different animal now that it appears metallic and weighs in at a solid four pounds, instead of its former bright orange and hollow plastic toy persona. Even though it has no functioning or moving parts, this thing looks and feels like it could take out an entire armored tank division in a few shots, and that's cool enough for me.