Actually light doesn't travel at the same speed, it's fastest in vacuum and slows down in the atmosphere, even more in water. The problem with that gun is that the barrel is placed too low, it does not extend past the trigger towards the back the rifle (same thing with the pistols, plus the lower barrel looks like it shoudn't be there). Those are cool looking weapons, but that's it. They are more cool than practical.
And high powered rifles may still be needed in the future as control singnals may be jammed, and the target may have armor on. Besides, this is still a game and people have to somehow identify with the elements inside. If we arm everybody in AO with cubes with short barrels pointing out at one end the game will be too wierd for anybody to enjoy.
From a pseudo-practical point of view the swords suck, too. Especially upgraded sword nr 2, I just don't see how you can effectively hold that thing in your hands and strike with it. Overall, the same trend: they are cool looking pieces of design, but don't look much like effective swords.