In Irish lore is a knife is facing up toward the moon then it is a sign of good luck.
The i seen a sight that said a knife pointing upward means danger. (i would go with this one. )
If you give a knife to a friend it will sever the friendship. to reverse the ill luck, you should repay them with a coin.

In other cultures, like finland, to give a knife is a sign of respect. 
Stirring liquids with a knife is unlucky.
It is unlucky to hand someone an open pocket knife.

a few more from a"Folklore what does it mean"

-A knife as a gift from a lover means that the love will soon end.

-A knife placed under the bed during childbirth will ease the pain of labor.

-If a friend gives you a knife, you should give him a coin, or your friendship will soon be broken.

-It will cause a quarrel if knives are crossed at the table.

-It is bad luck to close a pocketknife unless you were the one who opened it.

-Unless they are immediately straightened, crossed knives on a countertop or table indicate that an argument will ensue. 

-A steel knife was regarded as being protection against fairies and curses.

-A house could be protected by a knife being thrust into the door.

-A baby protected by a knife stuck into the headboard of its cradle (certainly not a recommended practice now!).

-A knife could also be thrust into the mast of a boat for luck, although the word 'knife' was never spoken at sea. 

-A knife falling to the ground means the arrival of a male visitor.

- Always open a knife before handing it to someone, Never return, or accept back a closed knife,its bad luck

-A knife with a white handle could be used to divine whether the enquirer's future spouse would be fair or dark. The knife was spun round, and if it came to rest with the handle pointing towards the enquirer, the spouse would be fair; if the blade pointed at them, the spouse would be dark.

-The dropping of a knife foretells the visit of a man friend in the near future. 

-A knife as a gift from a lover means that the love will soon end. 

-Dropping silverware causes company. Drop a spoon and the company will be female, drop a fork and the company will be male. Dropping a knife will break the spell. 

-Never give a knife as a housewarming present, or your new neighbor will become an enemy. 

Info from another site...on Folklore

* A knife as a gift from a lover means that the love will soon end.
* A knife placed under the bed during childbirth will ease the pain of labor.
* If a friend gives you a knife, you should give him a coin, or your friendship will soon be broken.
* It will cause a quarrel if knives are crossed at the table.
* It is bad luck to close a pocketknife unless you were the one who opened it.
* Unless they are immediately straightened, crossed knives on a countertop or table indicate that an argument will ensue.
* In previous centuries a knife was a very personal possession, carried at all times by its owner and used for hunting and work as well as cutting food.
* A steel knife was regarded as being protection against fairies and curses.
* A house could be protected by a knife being thrust into the door.
* A baby protected by a knife stuck into the headboard of its cradle (certainly not a recommended practice now!)/
* A knife could also be thrust into the mast of a boat for luck, although the word 'knife' was never spoken at sea.
* A knife falling to the ground means the arrival of a male visitor.
* A knife with a white handle could be used to divine whether the enquirer's future spouse would be fair or dark. The knife was spun round, and if it came to rest with the handle pointing towards the enquirer, the spouse would be fair; if the blade pointed at them, the spouse would be dark.

some guy did a site just for knife folklore and superstitions

http://www.jamesakeating.com/JakX.html