Please identify unknown insect
This appears to be a wasp. Could be a spider wasp, a predator of spiders. Also looks like a pipe-organ mud dauber, which makes the long tubes of mud to lay its eggs and store its prey.
Neither are aggressive toward humans, and they are beneficial since they eat other pest insects.
Here is information about mud daubers: http://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/non_HGIC_F...