Well this is more like an easter egg. On the "Traditional Trade" Level (not sure if thats the name of it but you will understand). There is a ghost. A ghost of the murdered man on the first floor on the north-western part. Find the room where a police man is taking a shower. Now look into the mirror on the bath room. You will see a ghost. (If you don't see it at first, wait a few seconds and it will appear)
(If you run around the corner when you are going to the room you can see the ghost go trough the wall and into the room)
In certain levels of Hitman: Contracts you can aquire a weapon called a Cardboard tube. It takes place of your Two handed weapon but acts like the Plasma Sword from Halo2, One strike regardless of position will kill the enemy and send them flying across the room.
The downside is that you need to be close to an enemy and it doesn't appear in all levels, however it is useful in dispatching enemies without wasting ammo, and there's something just so satisfying about killing an enemy with a melee weapon made from mashed paper.