Yes, I do it all the time. Not really to show off, but just because it is easier, more natural, and convenient for me. For one thing, it keeps the hands free to do other things like hold reading material or adjust my tie. (Quote from a friend in grad school who observed me flipping the pages of exam study notes while I was pissing at a urinal hands free but who was not positioned where he could see my penis: "How are you aiming?" I laughed it off, surprised at the realization that men with shorter penises need to use a hand to aim other than when writing their names in the snow. Never thought that much about it before.)
One exception: Being short in height, I have encountered a few urinals that are mounted so high they require me to hold my dick up--or even stand on tiptoe--to avoid having it draping over the rim--yuck! One was so high I even had to bend it up and over, like a periscope! (If you're wondering, no, that did not work very well as far as letting the stream flow.)
At the other extreme, in a BBQ joint in Texas I encountered a urinal that was mounted very low and had a sign over it: "For Kids and True Texans." That one worked just fine for me.
