This week I thought about how they could improve the game for the sequel, which I hope to God is being made as I write this, hopefully to be released in 2010. I thought of three things, basically. The first would be the shadows, that were somewhat pixelated in the original game. That definitely needs improvement. Another graphical issue is the aliasing, which can get pretty evident in some parts. They could increase the anti-aliasing if that didn't sacrifice the frame rate, and we would be thankful for that.
The last improvement in my view would be with the Plasma Cutter. It's the first weapon you get in the game, and frankly it's the best one overall. Even when I had many other powerful ones, I always went back to the Cutter. After properly upgraded it packs quite a punch, ammo can be found easily and it's great fun to use. I thought they could integrate it more to Isaac's armour in the sequel. Since he's an engineer, he could be shown making what I'm about to explain himself.
The Cutter would be integrated to his right arm/wrist/hand, staying above these parts, unassembled when not in use. When the player chose to use it, it would unfold around his hand, expanding parts that were collapsed, and it would instantly be ready to use. It would be visually nice, and gameplay-wise it would make the Cutter something similar to the pistols in Left 4 Dead or the revolver in Killzone, for instance. Definitely not powerful weapons, but ready to use in case of emergency.