Not nearly enough love for Gears of War 3 in here. You guys do all know that Horde is called Horde because of this series, right?
This game perfected Horde mode. Let me tell you what it does that no other game (including Gears Judgement) has done since. Each kill you get earns you money that you can spend between rounds on a number of options.
Building Fortifications
When you start a game, you have 5 or 6 bases to choose from on any given map. Pick the one that seems like the best spot for your team to dig in, and from here you can start to assemble a fortress.
-Barbed wire and Laser Fences for keeping the enemy out. Pay to have them repaired each round (if they take damage)
-Dummies for distraction. Can ultimately be upgraded to a full-blown AI teammate that fights alongside you for as many rounds as it takes them to die.
-Mounted machine-gun turrets. Create choke points and bear down on the enemy with heavy damage and pay to have them reloaded between rounds.
-Air support. Build a terminal that calls in snipers, mortars, or orbital strikes. One-time use per purchase.
-Extra weapons Self explanatory. Your favorite weapons are scattered around the map, waiting for you to buy them if you don't want to wait to take one from a fallen enemy.
-Automatic Turrets Just what it sounds like. Upgradeable to eventually deal electric and fire damage.
So through all of these things, you can have a hallway set up where you have mines(planted grenades) at the entry way, a lazer fence slightly past that, and a turret bearing down on the enemy when they get caught in the fencing. Its really satisfying and leads to all these decisions about how you want to spend your resources and where you want to focus your firepower. If you want, you can eventually expand outward and establish every base on the map, or just decide to stick with one and make it the Fort Knox of bases.
Boss Waves
The game has 50 waves of enemies total, but every 10 waves there is a boss thrown into the mix. Shit gets nuts when you've got a dozen locust drones laying down fire and suddenly a Brumak arrives on the scene. The feeling of accomplishment after every 10th wave has not been replicated in any other Horde mode for any other game.
In it for the long haul
If you're a serious Horde player and you want to get through all 50 waves, expect to play for 2 1/2 to 3 hours. Its a marathon of teamwork, frantic action, and high fives. Its too bad the online community has died off so much, and especially that Judgment ditched Horde altogether for the ultra-shitty "Survival" mode. When you can find others to play with who are dedicated and won't quit 4 rounds in, this is amazing. I really hope they bring it back for Gears 4. If you can ever do a LAN for this, I highly recommend it. We did it earlier this year at Midwest Gaming Classic and it was on fire.
So there you have it. Take it from somebody who got obsessed with Horde. My team broke Top 50 on the leaderboards for several maps, so we had it all down to a science and its still not old for me. Sure, I play other games too, but Horde in Gears 3 will be one I go back to for years to come, even if sometimes I have to play alone and see how long I can hold out.
Also, a quick nod to FEAR 3's "FUCKING RUN" mode. Its like Horde on the go where you're scrambling to get from point A to point B while Alma's wall of death closes in from behind.