Cambridge shamrock
When, on St. Patrick's day (or night), a guy living or staying in Cambridge blows his load on his girl, preferably her face, while simultaneously flinging a handful of bright green glitter at her so it sticks to the jizz.
Yeah, we fucked for a bit, but when she asked me to turn off the Dropkick Murphys playing in the background I had to give her a Cambridge shamrock.