A sake bomb is a fun drink to enjoy at your local, and hopefully very gaijin-tolerant, sushi bar. It's a Japanese-themed equivalent to the boilermaker; replace the whiskey with some nice warm sake, select a good Japanese beer to go with it, and you've got the idea. If you want the full experience, a quail egg can be added to the sake glass.
Now that you have the ingredients, it's time to drink! Place your chopsticks across the top of the beer glass, and carefully balance the sake glass on top of the sticks. When everybody is ready, bang your fists down on the bar, dropping the sake into the beer. Slam the resulting drink, taking care not to let the sake glass knock out your front teeth. Ignore the stares of the less enlightened patrons.
Enjoy, and watch out for those teeth!