Wikileaks, though technically not a wiki, provides an easy means to disseminate information that some find it desirable to share against the wishes of those who find it desirable to keep secret. Aside from the morality of the leaking itself, such a service provides a look into the activities of...
Don't stay in one place for too long if there are snipers about.
You can jump back towards walls you've already jumped off to avoid obstacles.
In the end-of-level scraps, take out anything with a gun before you deal with the others.