The AR was made for muzzle devices. That is why there is threading at the muzzle, instead of a smooth polished muzzle like on your old wood and steel hunting rifle. It is practically asking you to put something there. The AR market responded to that question with literally hundreds of viable answers. There seem to be more different kinds of muzzle devices than any other single AR part. So which one should you get? 
     Which kind do you want? I mean in general. There are sound suppressors, flash hiders, muzzle brakes, and compensators. They are good for many different things, and there may be times when you want to switch one for the other, depending on what time it is or something. 
     You might want to start with the tried and true. One of the most popular muzzle devices is a classic called the Birdcage. It is a flash hider that has been used by the military for many years now. Flash hiders are for hiding the flash from you, the shooter, and if it hides it from anyone else that’s ok too. This makes it so you aren’t temporarily blinded from the flash of your shot, allowing for better follow-up shots. It is especially useful in low-light situations, so that time of day might come into play with this. You can find these pretty much anywhere for a low price, that’s the advantage of something this popular and time tested. (Flash Hider) 
     If you want a Birdcage with extra, we have a more -ahem- flashy version of this that is completely stainless steel. (Flash Hider) 
     There is the Blast Can which not only reduces recoil but directs most of the blast forward away from your face, perfect for AR pistols with shorter barrels. (Linear Compensator) 
     The Recoil Technologies Knurled Linear Compensator Muzzle Device moves the blast away from you, great for AR pistols. (Linear Compensator) 
     The Midwest Industries .30 Caliber Blast Diverter Steel Parkerized is a Linear Compensator. This diverts the muzzle blast away from you negating muzzle rise and making it a bit quieter for you and those near you. (Linear Compensator) 
     The Muzzle Innovations B-Sting Muzzle Brake will reduce recoil, and yeah, it kind of looks like a bee stinger. (Muzzle Brake) 
     The VG6 Gamma hybrid is a muzzle brake and a compensator so it will reduce recoil while also mitigating muzzle rise. (Muzzle Brake/Compensator)  
     The VG6 Precision Epsilon looks like a tactical rook. It is a hybrid muzzle brake, compensator, and flash hider. It compensates for muzzle rise and recoil as well as being a decent flash hider. A great all-around hybrid. (Flash Hider/Compensator/Muzzle Brake) 
     On the fancy overachiever side of the spectrum, we’ve got the Primary Weapon Systems .223 Tactical Compensator Mod 2. This is a device that is fairly unique, with a bigger price tag to boot. It is both a flash hider and a muzzle brake and does both pretty well. (Flash Hider, Muzzle Brake) 
     These are just a few of the many muzzle devices we have, not to mention the hundreds of different kinds the many producers provide. If you want a different experience with your AR, a muzzle device is an inexpensive way to do that. They are easily interchangeable, so swap em out with your buddies, and find out which one works best for you. Just be aware you may have to re-zero when you change most anything. The more you try the better informed you’ll be. Just remember there is no wrong answer to muzzle devices, just the best answer for the right question.