A male quaker
The Quaker Parakeet (monk parakeet, quaker parrot)
Myiopsitta monachus

Size: Approximately 12"
Weight: Normally 80-110 grams
Lifespan: 30 years
Natural diet: Granivore
Native to: South America

Min. cage dimensions: 24"x18"x18" (larger preferred)
Bar spacing: up to 3/4"

Handling needs: Quakers are extremely social animals, they even nest together! You must spend at the bare minimum one hour a day with your quaker to keep it happy and tame.
Sound Level: Moderate to loud. It is uncommon to have a quiet quaker. In general, they will scream and talk incessantly throughout the day.
Talking Ability: High. Some quakers have vocabularies of a few hundred words. They speak clearly and can use words in context.

Special notes: Quakers are illegal in many states (like Kentucky), whereas there are only some restrictions in others. You must check an updated list before considering this type of bird. Quakerville maintains such a list here: http://www.quakerville.com/qic/statelaw.asp.