I certainly have. Like exw, it's a trick I've enjoyed doing for myself since I was a kid and for girlfriends since I was old enough to have them. Related anecdote: one of my close friends--who has some inkling that I am larger than average but doesn't know the full picture of my actual size--once remarked about seeing Ron Jeremy doing this in a video and being really amazed by it. I just chuckled inside and said somethink like, "yeah, that must be really impressive."

As to the original question, I normally hang at least 7" soft and wear boxers and loose fit pants, so, yes, I jiggle and flop as I go about my daily business. It's an enjoyable sensation when I think about it, but I usually have no real awareness of it since I've had a long, floppy penis my whole life and basically take it for granted.