The most recognized item for have pleasant dreams is naturally the dream catcher. Some places in Eastern Europe may use a key. A favorite among children is the Worry doll. That is a great concept; pass on all your worries to the doll and have happy dreams. The peridot gemstone has a reputation for keeping nightmares away. Just make sure it never ends up in your bed. Keep it in your bedroom, close to your bed. An alternative to peridot is the ruby which also should keep nightmares from taunting you.