Take items from one of the characters you have and give them to another character. You however cannot do this by yourself (without danger of losing your stuff) because you can only have one character active at a time.

Like, I have two assassins, one of whom has Bartuc's Cut Throat greater talons. I want the other assassin to have it. So I can go into a game, drop the claws on the ground, leave the game, enter the game with the other assassin, pick the claws up, and they are hers. However, this is dangerous to do by yourself because your game is likely to go away in the time it takes for you to log off and back on, and the stuff on the ground goes with it. But having another person there negates that danger because the game won't close (unless that person lags or something, but in the time it takes for someone to lag you can probably log off and back on safely).