FlipSilent. OK, so you’ll need a Symbian S60 handset with an accelerometer for this (Nokia N93i and N95 only at the moment?) but it’s still very cool nonetheless. Install it and you have the power to turn off an incoming ringtone just by flipping the phone over. You can also set it up to switch into silent mode when you flip the handset over, which makes it useful for meetings (as long as you remember to take the phone out of your pocket of course). Oh and it’s freeware, which is nice. Take a look at the short demo video.
A small software which makes you use your phone in a more natural way: When you are in a meeting or dating, and a call is coming in, you can flipover your phone to make it go into the silent profile and hang up the phone call or mute the ringer — without touching anything on the phone, just flip it over, your phone will go into silence!