For those born without a sense of humour, Halopedia has an article on Type-50 Sniper Rifle System.
Cquote1Pretty lights...Cquote2
— Random noob before being killed by a Beam Rifle
Cquote1Why the heck do all snipers have trails following the shot?!Cquote2
— A typical Halo player with a valid point
N'tho 'sraom

"Oh god YES!!"

The Beam Rifle is a long-range Covenant weapon used mainly by noobs. The Beam Rifle is very long and purple, which makes it look more like some weird alien dildo than an actual rifle(Japan loves the idea). It is supposed to be much more powerful than the Sniper Rifle, but it emits a bright purple beam whenever somebody fires it, and it overheats after only two shots so it burns your hand. Needless to say, only noobs have the audacity to use such a shitload of fuck.The most recent models shoot silly string instead of LAZ0RS. This silly string can be deadly to Master Chief as it gums up his armour and makes explode. Said silly string is a licensed product of Covenant, Incorporated™ and cannot be sold without their permission, unless bought from KY toys, in which case use with caution. (Covenant, Incorporated™ is not responsible for death by its "Webs of Bicuriosity"® product).

Who Would Use This Thing?Edit

I'll tell you who- fucking Jackals. For some reason, jackholes think that they can use it and be as cool as a human sniper, and that they never have to reload like a human gun or that they can just shoot a human who was trying to get a Killtacular! That's NOT FAIR, DAMMIT!

In any case, the turkeys use these weapons frequently, especially when the target human is at a medium-to long range distance. 
Halo 4 beam rifle

Finally, in Halo 4, the Beam Rifle doesn't look like a vacuum cleaner!

Melee Weapons: Kitchen Knife | Japanese Butter Knife | Taser Stick

Handguns: Comfortable Pistol | Another Comfortable Pistol | WTF no scope? | M6C/Suck em' | God's Sidearm | Safety Mode On | Trusty Sidearm | Trusty Sidearm 2: Gradius | Assassination Pistol | Carbine Pistol | Silenced Pistol | Orbital Airstrike

Automatic & Semi-Automatic Weapons: Bullet Hose | Silent Bullet Spitter | Insult to Rifles | Revised Insult to Rifles | Chronologically Confusing insult to rifles | The insult to rifles that actually kicks ass | Bee-Arr | Bullet Spammer | Another insult to rifles | Large Bullet Hose

Other: HEADSHOT! | Pest Control Tool | Mini Missile Silo | Rocket Lawn chair | Splazer | Campergun | Noob Obliterator | Crude Thumper rip-off | Supersonic Rail Exploder | Exploding Cake Detonator | Kill The Hydra

Grenades: Damn, no stickies | Bang Grenade | Ear Bleeder | "I embrace y'all with napalm..."

Melee Weapons: Energy Shank | Hot Poker | Death Stick | Energy Shiv | Gravy Hammer | Monkey Fist | Monkey Shank

Other: Peashooter | Overheated | Angry Plasma Rifle | Overheater | Noobler | Larger Noobler | Long range Noobler | Nailgun | New Noob Combo | Rock Slinger | L337 5K1LL5 | Follow the pink light | Vacuum Quadlazer | Jelly Launcher | Semtex Blue Spider | Stick-rock | Fire in the Box

Heavy Weapons: Mini Blue Jelly Factory | Death impersonated | Godly Plasma Rifle | Huge Water Gun on Spaceships | Hax Gun | Smaller Hax Gun | Derp Gun | Magic Grenade Thrower

The Quadlazer | Zapper | Tracer Rifle | Yellow Light Spammer | Campergun's Retarded Brother | Triforce Gun | Promethean Glory | Forcefield | Bee Grenade