Quote:
At the bar, just shout GARCON !
Or just wave your money at them - remember it's you that's invisible, they can usually see money quite clearly. Works quite well for me. Not that I need to do that very often - if the bar's that crowded, I'm in the wrong place.
When it's people trying to walk through me, I sometimes just stand still in a place where they'll have to either bang into me or plot a new course. It seems less confrontational than just continuing to walk regardless, and hopefully they look more like the guilty party.
Loads of people try to cross the road in front of me when I'm cycling. I used to have an extremely loud hooter which I would use to - er - warn them of my presence - the loudness was somewhat unnecessary, but there's nothing like a short, sharp shock for getting the message across. I rather think some of them probably took a little more care next time, which may even have saved a life or two.