Welcome. Post everything and anything you want to see in Gears 3. But for goodness sake, "no more glitches", "less lag" and "better everything" is just silly.
Oh, and SPOILERS. So be prepared.
Here's my ideas:
Sticking grenades to meatshields and pushing them forward so they flip over cover. Or just being able to use grenades with meatshields/boomshields. But I really like the Meatbomb idea.
Tweak the specific angle and distance for picking up a meatshield. Rolling past them because you didn't stand still for two whole seconds before pressing 'A' is annoying.
Kantus Zealots - they wield chainsaws and some sort of grenade. Extremely dangerous, because they are suicidal and fast. They can be slowed down by bullets, but their jumping ability allows them to somersault over cover and get behind you if you're not careful. If you stun them and then chainsaw them, you circumvent the need to duel them.
Seeder boss-fight. Since the Hollow is flooded, the surviving Seeders must be used above ground, maybe from a building. And remember the Seeder you see whilst being chased over the forest in the Reaver level? Just imagine fighting a beast like that. The fight would be fast paced, mostly about dodging the attacks and trying to get underneath it to attack the soft underbelly. However, the Seeder can scuttle away and climb up nearby walls, then jump down on top of you.
Mawr berserkers. But instead of using the hammer of dawn on them, maybe it could be a boss battle where you have to trap it, or collapse a building on top of it. I like the idea of being able to trap it, and then show a quick cutscene where everybody converges on it and blows it's face apart bit by bit with shotguns. An even better idea would be to kill it with "gutpuncher" grenades from close range (see below).
Gutpuncher grenade-launchers. If you have a lancer or hammerburst, you could stick a gutpuncher on the end and shoot it through certain walls. Can penetrate armor. If you've read the Gears book, Aspho Fields, then you know what gutpunchers are. Maybe you could screw them into the barrel of the gun?
Pilot a King Raven as one of the game's highlights. Maybe an epic boss-battle against the Queen? You should be able to fly freely, but if you get past a certain point you'll start attracting a plethora of Reavers and Nemacyst. Player 2 controls the minigun. Just imagine seeing a bunch of Locust in a building and having to do a quick spin to come back by with your gun-turret side facing them, so Player 2 can work them over. If playing by yourself, Dom could control the turret, or you might be able to switch to it and let Dom pilot the thing, though that might not work out.
Some type of worm enemy that is driven out from the underground by the seawater. Rockworms would probably come up too; just imagine a half-sunken city. You're moving down the street, and suddenly you see a rockworm come crawling out from behind a building up ahead. But the worm enemy would probably be more dangerous, as in working against you and not staying neutral.
A worm bossfight. No, not on the inside of a worm, but an actual bossfight. Gutpuncher grenades could be used to blow it up when it rears up. Or maybe, a bossfight that includes a BUNCH of huge worms, and only ends when you've killed them all. So a multi-boss fight.
Closure for at least one Carmine brother.
Clay should be some sort of badass. Or maybe D Carmine could be badass and Clay gets killed. Or vice versa. Any number of things, but we want a kickass Carmine!
Now post your own ideas. Seriously, we need them.