One that stops little kids from talking.

It would be a bigass bazooka that when you shoot it a flag with the word "irony" on it pops out...then the enemy spontaneously combusts.

What about a gun that attachs to an enemy and then to a wall (with a second shot) or perhaps to two enemys and then contracts.

A gun with a chainsaw on it!

yeah, something that shoots the various grenade types would be awesome.   can you imagine an accurate plasma grenade launcher?

A gun that inverts enemies controls when you shoot them.

Instead of a gun, how about jackal shields? Ha. Yeah, no. Probably not a good idea. Chief's way too big for those anyway and it would just look silly, but considering we've seen them in every Halo game, it kind of makes you wonder why we haven't been able to use them yet. We got the bubble shield instead, which is far more awesome. Heh, what if you could use them for cover and also throw them like Captain America shields? That could be pretty outrageous. It'd be like MW2's riot shield and throwing knives combined!
 
I'd like to see more creative weapons in Halo Reach. Most of the covenant weapons are pretty darn original. I think the needler is probably the coolest one conceptually. I also love that freaking Brute Shot, man. It's also not very popular, so usually it's up for grabs when you play online. Most people don't seem to realize how awesome and effective it can be. Hmm.... I wonder if there are any other weapons in the Halo series that have been around but never used in multiplayer. Take the sword, for instance. It was in Halo 1, but couldn't be used by players until Halo 2. There was the sentinel beam and flamethrower, which were limited to custom matches, but I can't think of anything else. Oh, the hammer used by Halo 2's boss that became available in Halo 3. Well, judging from the way things have gone, if there's any weapon in Halo 3's campaign that could only be used by enemies, odds are it'll be available for Master Chief to use in Halo Reach. There's also the Fuel Rod Cannon which has never made it into multiplayer for some reason.

" A power full single-shot rifle kind of like a M1 Garand and a grenade launcher attachment to the AR.  "

a gun that shoot aids. yes, aids...

A gun that shoots guns which shoots guns which shoots bananas which shoot penises.

Medic gun.

How about a gun that shoots pants?
 
Or maybe a gun that is really a hand warmer, it just looks like a gun. But it will also be a jaw-breaker dispenser too.
 
Creative enough?

A gun that shoots gum.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Which then promptly explodes.

"What about a gun that attachs to an enemy and then to a wall (with a second shot) or perhaps to two enemys and then contracts. "

"A power full single-shot rifle kind of like a M1 Garand and a grenade launcher attachment to the AR.  "

A gun that shoots energy swords.

Alien shotgun would rule!

" One that stops little kids from talking. "

I like the idea of a single shot rifle but you have to mount an Energy Sword underneath the barrel of the gun as a makeshift bayonet.

A bolt action Brute Sniper rifle that has a small-ish clip and can pin dudes to walls.  As par with any Brute weapon it's gotta have a big ass blade on it somewhere... maybe a Bayonet on the front of it.  

No wait, I change my mind, I want a portal gun.  That shoots energy swordsandportal bullets.

A gun that lets you shoot yourself in the head, summoning Master Chief, whose shoots bufu from his gun.

Cerebral Bore please.

a gun that nukes the map and disconnects every player on every Halo game from xbox live

" One that stops little kids from talking. "