It was the lovely and charming Emily Dexter (with whom I used to work, at the Sea Dog)!
After talking with her a bit, Stephanie duMysterioso showed up -- that's not really her last name, but it's a little thing I think to myself when I'm getting to know someone rather well but haven't found out what their last name is. Now, Stephanie is pretty big into high-fiving folks, and into punching me in the shoulder as a form of greeting. Last time I talked with Stephanie (about basalt pillars and suchlike), she decided to teach me a 'tell' when folks are high-fiving you. Namely, to look at the elbow and not the hand. Funnily enough, since she pointed that out, I was able to use it in practice and I saw it cited in an episode of The Guild (when she's hanging out with the stunt guy neighbor). I mentioned this to Stephanie, which got Emily to wondering what we were talking about, which prompted Stephanie to demonstrate. She showed that it worked for a standard "attack", as well as off at an angle, and even (...this is where my Spidey-Sense started to tingle...) at an extra-oblique angle.
Ok, so Emily is seated on my left, Stephanie is standing on my right, and I'm standing behind a barseat with my elbows resting on the back of the seat and my glass on the bar across from the seat I'm leaning on. As my Spidey-Sense detected, Stephanie's extra-oblique angle took out the stout glass.
It was a very nice clean flip, and it landed perfectly upside down on the seat in front of me. Yes, this meant that the contents of the glass (an entire pint save for three sips) ended up on the seat, around the seat, and drenching me from mid-thigh down.
Stephanie found it impressive and amusing that my reaction was, eh.. nothing. I basically just watched it fall, and perked my eyebrows when it landed upside-down so very neatly. No yelping, no jumping back, no nothing. Once she finished laughing at my (non-)reaction, my reply was, "There's worse things I could end up smelling like than Guinness, you know"