The point of shotguns mostly in teamplay matches IS for the snipers (who aren't allowed to shoot anyone within 100 feet) use the shotguns and usually just strap them to their backs. The Desert Eagle FPS is generally so low, because of the weight of the slide, needing more power to just blow the slide back more than anything else. Green gas is the type of gas, that allows most guns their blowback feature, co2 isn't strong enough. The grenade launchers are really nice. They shoot cartridges packed with bb's, and when they hit something all of the bb's spray out. For types of guns I recommend Classic Army, Tokyo Marui, or ICS. Those are brands you can trust, and they sell the best guns at a reasonable price.
If you want to know what I have, I carry with me an ICS AK-74 (yes a 74!) and a KJW Glock 18-C Full auto. I'm satisfied with both, especially the range i get and how much fun a full auto pistol is. Every once in awhile I'll carry my Sawn-off shotgun for laughs when i get a headshot.