Regarding personal anecdotes, my first girlfriend would stand in front of me, throw her arms around my neck, lean her forehead against mine, and dance from side to side while gazing into my eyes (usually in public as I recall). Despite never before having a girlfriend, for some reason this annoyed me, and now it's hard to understand why. I can only recall thinking that she was acting silly, and from months of corresponding with her, I had an impression of her as a very serious young woman, and this sort of behavior surprised me.
As for more flagrant acts of PDA, I can think of 2 in particular. So this one girlfriend I have mentioned before who was sort of a MPDG (me 24 her 21), one day I and a handful of people (including at least one couple) were sunbathing on the roof of a house I was living in. She showed up, and although I can't recall much detail, she basically started making out with me with the unmistakable intent to get me sexually aroused, so I would go back inside with her to have sex (she had in fact brought a condom with her). I was a bit embarrassed at the time, but then I probably thought that, after years of being single in both high school and most of college, I could live with having the reputation of being in a relationship with somebody who flaunted her sexuality so publicly.
A handful of years of experience later, at age 28, a young woman I had met at work (age 22) had asked me on a date. Basically we hung out at the Columbia Maryland lakeside (I can recall we took a paddleboat out). At one point, we were sitting on the grassy lawn that sloped down to the lake, and she suddenly pounced on me and started aggressively tongue kissing me as though we were somewhere private. At first, I was very self-conscious, but then I considered that I would have given anything to be in that situation when I was a teenager, and better late than never (to me she seemed a very young and inexperienced 22 but after all it was she who wanted the date).