UPDATE: Added a note next to each plasmid, indicating which powers appear in single-player, multiplayer or both.
"BioShock 2" takes place ten years after the events of the first game, and in that time it appears that freaky, mutant, underwater scientists have managed to create some nifty new powers. I've spent some time with an early build of the game, and I thought it might make for good preparation to detail some of the new plasmids (along with some of the upgraded classics) you'll find in the heart of Rapture.
Scout (Single-player Only)
An extremely unique plasmid, this allows you to basically turn into a ghost at will. In "ghost" form you're invisible, but you can still use attack plasmids (no guns, though). This means that you can scout ahead and zap unsuspecting splicers standing in a pool of water, or temporarily deactivate pesky turrets without threat of attack. Your physical body will remain in the same place, though, and you'll have to return to it to progress.
Hypnotize (Single-player Only)
The first game had a plasmid called "Hypnotize Big Daddy." Same idea here, except it'll work against ordinary splicers at a much lower eve cost. You can actually charge this power up, granting you dominion over an angry splicer for a longer period of time. It's not permanent, though. After about 5 minutes the power will wear off and you'll have to make short work of your new best friend.
Aero Dash (Multiplayer Only)
In multiplayer you can use Aero Dash to give yourself a burst of speed. If you charge into anyone you'll do serious damage. It also makes for a great way to bolt if you've managed to snag a Little Sister in the game's CTF-esque mode.
Cyclone Trap (Single-player Only)
One of the returning powers. Cyclone Trap works the same as it did in the first game at level one. Power it up to level 2, though, and you can charge any cyclone trap with another attack plasmid. So, for example, you can set a trap and then shoot an Incinerate! plasmid into it. Then, when anyone activates it, they'll be thrown into the air and set on fire. Handy!
Electro Bolt (SP & MP)
Just as in the first game, this is the first plasmid you'll find in "BioShock 2." It acts as normal (stunning foes, leaving them open for a melee attack) until you power it up to level 2. At that point you can charge Electro Bolt and release it, causing chain lightning across any enemies nearby.
Incinerate! (SP & MP)
As with Electro Bolt, Incinerate! acts the same as it always did until you power it up to level 2. Once you do, you can charge it up and release for a "fire bomb" attack, great for setting whole groups on fire.
Winter Blast (SP & MP)
Level one's the same as before, but level two will allow you to charge and release for an increased ice attack. Foes in the blast will not just freeze: They'll turn into blocks of ice. This will keep your foe frozen for longer, and the ice block can even be used as a projectile when lifted with Telekinesis.