The camera, once you get it, should be used very very heavily. Unlike in SS2 where research primarily gives you small damage bonuses, you can get some very, very nice bonuses from researching enemies the whole way.
Little sisters give you a small health and max bonus for every level of research. Bouncers include a 50% damage bonus to everything you hit with the wrench - which, combined with a couple of the right tonics, can turn you in a doomsday wrencher.
The various splicers each tend to include a couple of helpful tonics in the research rewards, and the turrets and security bots both become instant hack success at the highest level - very very convenient.
Houdini splicers eventually yield the cloaking tonic, which is very very useful if you're playing stealth.
The audio logs, while have been generally very high quality, has one that sticks out in my mind more then any other. It's as creepy as Korenchin's Glory audiolog from SS2.
..edit: Edited out spoilers, since [spoiler] doesn't seem to work. Someone remind me the code for spoilers?]
Bookmarks