It's not as if anyone really needs an excuse to head out to Vegas for the long Memorial Day weekend, but for folks of a punk rock persuasion those dates have been marked on the calendar in indelible ink, like a stick 'n' poke tattoo. Celebrating its 21st birthday — and legally old enough to get hammered — Punk Rock Bowling has grown over the years from a fun little get-together with a handful of bands to a full-blown festival that is arguably the finest of its kind in the world.