Condemned Hex Cheats
Keep in mind for this one You'll need to edit Your savegames in order to be invulnerable and You'll also need a Hex Editor (Hex Workshop). Make a copy before You do it.
Go into your install directory (default is: C:\Program Files\SEGA\Condemned - Criminal Origins) and click on "view the player data folder". After, go to Save/Profile000/SinglePlayer. Select the savegame on wich you want to be invincible and open it with a Hex Editor (Hex Workshop). Once it open locate this line (not very far from the beginning) DemoModeInvulnerable..0.000000
change it to DemoModeInvulnerable..1.000000 (as you can see you replace the first "0" by "1"). Save the file. Then you can load this savegame and you will be invincible.
You can drop important weapons and tools near distinctive objects or in easy-to-find spots. Once You do this You will not have to search for them later.
Bare in mind sprinting is not that useful on stairs. Save it for level surfaces.
Big melee weapons
Want to use big melee weapons!? Good way is to practice hanging back, then veering ahead far enough to hit your enemy with your weapon. Then, drift back. This makes the most of Your weapons' superior reach and keeps you away from your opponents' faster weapons.
It is best to save the revolver for fights against multiple enemies (or against exceptionally tough loners). Particularly weak enemies can be finished off with a combination of Taser and kicks instead.