How to give the knife or sword to the human.

hey for testing purpose i was using the character used in 3D person shooter game. Can i give him a sword or knife instead of gun. thanks in advance.

Yes you can.

Check out Duck's answer here: http://answers.unity3d.com/questions/5714/equiping-weapon-to-a-character

And Lucas' answer here: http://answers.unity3d.com/questions/1177/character-customization