Hitman: Blood Money Hints & Cheats

On the opera house mission, in the basement at the back part of the stage, there is a room that leads to staircases to bathrooms on the first floor. After heading down the stairs there is a room you enter, kill the three rats on the ground and check the bench at the end of the room. There is a keycard for the rat club. Head to the second level where you collect the lightroom keycard. There is a door that cannot be opened. Use the rat club keycard and in there are rats boxing and gambling.

When in the middle of a mission and you're in the process of saving, repeatedly press the start button, and after it's done saving, the number of saves won't lower.

When next to a window you can't seem to really get past, bring up your map and then go back in-game and 47 should climb through the window.
Note: Sometimes you have to be touching the window.