You've been buying your own booze at the local bar like a sucker ever since you turned 21. But with a stiff shot of science, you can hustle the tipsy into picking up your tab. Try this pub magic to score yourself some free rounds. €” William Snyder
Wired has a nice wiki page about some different Bar tricks that you can do to win yourself a free drink or two. DO Bar Tricks
There is also a great YouTube Video, 1000 different ways to open a beer bottle.