Uncountable Alien
I've gotta give another BOTB shout-out to the most amazing bird I've seen in the United States thus far this year: the black-throated magpie jay. There's a small number of this species that lives along the San Diego/Tijuana, Mexico border. They are probably there as a result of some bird smuggling gone awry or as escaped cage birds. They are native to west-central Mexico, but have begun breeding in southern California. They are not countable now for North American bird lists, but methinks it only a matter of time....
Countable or not, this bird can make even the most jaded birder go "Wow!"