A very hilarious use i've found for force pull is on maps with a lot of pits and such where people try to force grip level 3 you into holes. When you're behing held above the hole, just as they drop you, you pull them in with you LOL
I'm sorry but even though you still end up dying, bringing them with you is worth it
As for pulling guns, i've found that you sometimes need to pull several times before the gun comes loose, but it does work. They made it work this way i think, because they dont want force pull to work like in single player where you can disarm a whole room full of enemies in one shot, every shot.