-developer -developerkeys -screenshot
What are they?
-developer:
This enables the console. These are usual commands(cheats..)
code what does it do?
god immortal
mortal mortal
get<gun> gets you a gun named at <gun>
getall gets you everything
gethealth you get fully healed
showfps (put -developerkeys and push F1

-screenshot
You can get a screenshot by pressing F10. Screenshots go to Max Payne\screenshots
-developerkeys
When your in-game(and I suggest in pause mode), press c and you can move around the level. If you want to take a screenshot from a place you've chosen, just press F10 when you have -screenshot on.

What -screenshot? Where do I add them?
-When you start max payne, add -screenshot, -developer or -developerkeys after maxpayne.exe
:)