Choose one person to be "it" and define the boundaries in which the rest of the group can run around. Give an object (a ball, rubber chicken, etc) to someone in the group.
"It" can tag anyone, as long as that person does not have the object in their possession. The group works together to pass the object to the person being chased by it, which prevents them from being tagged.
When "It" tags someone, that person is out and sits (patiently, of course) outside the boundaries. The game ends when only one person in the group is left.
A couple variations...
Generally, "It" can't not block or catch the object, but you can certainly change that rule. Also, you can also allow any tagged person to become an additional "It."