Bioshock 2

- When you're outside underwater, keep your eyes peeled for ADAM slugs. About half of them are very obvious, and the other half are poorly-hidden. If you speed through the level you'll miss them.

- It's worth hacking every vending machine you get just for the potential hack darts (as only hacked machines will sell the darts). If you're full up on darts, it's still worth hacking them because if you hit the blue area during the hacking minigame on a vending machine, you get some free items from the machine.

- Use the roving Big Daddies to your advantage during tough fights. The game's pretty good about telling you when there's about to be an onslaught (there's a guaranteed mob event every time you gather ADAM with a little sister, and a guaranteed boss fight with a big sister when you rescue/harvest the last little sister in a level), so try to position yourself near a Big Daddy right before these things happen. With any luck, the splicers/bosses you're fighting will accidentally hit the neutral Big Daddy who will turn hostile on them and take a lot of the focus off of you. The caveat to this strategy is that later in the game as mob events and boss fights become more hectic, the odds that you'll be the one to accidentally hit the Big Daddy will drastically increase, and fighting a mob AND a Big Daddy can be very tough. If you're having trouble luring the enemy to a Big Daddy, or if the enemy is being careful not to attack the Big Daddy, you can upgrade Hypnotize to level 3 and then just charm the Big Daddy. Then he'll attack anything that's hostile to you on his own.

- Many enemies charge during combat (brute slicers are the worst, but Alpha Series, Big Sisters and some Big Daddies will do it as well). You can stop them by meleeing them (doesn't matter with what weapon) right before they strike you. They'll get disoriented and you can get a few shots in, or just run away.

- You can find the research camera in Pauper's Drop, in the pawn shop. I recommend getting it before you do ANYTHING ELSE in the level, just so that you can maximize your research ASAP.

- Along those lines, two of the research perks are worth obtaining immediately. The Scrounger (fully research Thuggish Splicers) tonic will massively increase the amount of loot you find, and it creates new random items and containers when you backtrack through a level, which is pretty awesome. The Natural Camouflage (fully research Houdini Splicers) tonic will let you turn invisible while standing still, which is handy for hacking and defending little sisters while they gather.

- During a research session, you get the best bonuses by bringing in allies. So try to lure enemies to areas where you control cameras and turrets, summon bots, use the Hypnotize plasmid to turn other enemies to your cause, and trick enemies into enraging a Big Daddy (by standing right behind the Big Daddy during a fight). The other way to stack up good bonuses is by using environmental hazards. So electrocute enemies standing in water and light enemies on fire who are standing in oil patches or near gas leaks. You get far better bonuses for these things that you would for just switching up plasmids or weapons. For the record, you get about a +100 research bonus during a session for each time you use a different plasmid, and maybe a dozen points each time you switch weapon types. The most effective plasmid (at least in the context of research bonuses) is TK. For whatever reason, you can rack up huge bonuses by throwing things at the enemy, throwing the enemy at things, and throwing things that the enemy threw at you back at the enemy.

- Don't remember if this was in Bioshock 1, but here's the neat thing about telekinesis in 2: Pulling items toward you costs no EVE. You can drop an item you've pulled toward you by hitting square. Dropping items doesn't cost anything either, neither does searching a container you've pulled toward you. The only part of telekinesis that costs EVE is when you throw the item. So with TK3 you can pull a live enemy toward you, and while you hold them there you can bash them to death with your melee attack, then drop the body and you won't have lost any EVE.