Test:

test("unbind(event)", function() {
	expect(3);
	var el = $("#firstp");
	el.click(function() {
		ok( true, "Fake normal bind" );
	});
	el.click(function(event) {
		el.unbind(event);
		ok( true, "Fake onebind" );
	});
	el.click().click();
});

Implementation:

Within the for loop in handle:
event.handler = c[j];

Within unbind:
if(type.type && type.target) {
	jQuery.event.remove( this, type.type, type.handler );
} else
	jQuery.event.remove( this, type, fn );