I loved the stealth sections. It was great lurking in the shadows, and picking them off one by one, watching them slowly getting more terrified. Maybe I'd mess with them as well, pick on one by chucking a few batarangs at him before finally taking him down and leaving him for his buddies to find. It's also great when you can properly lay a few traps, with exploding walls and such. The fire extinguishers also make for a great distraction.
When there are multiple guys with guns in small spaces, you just have to be quick when making your move. Pick a guy, take him down, get out before they all converge (there is usually somewhere to go that they cannot see/reach), repeat. Make use of the batarang upgrades so you can stun 2 or 3 at once if necessary, and then take down the guy (or guys) who go to see what happened.
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