Current Apple mouse:
From: http://www.apple.com/mightymouse/design.html
The Button That Wasn’t
Alas the fate of the one-button mouse in today’s multibutton world. Who has time for intuitive, elegant design when there is so much clicking to do? Thanks to a smooth top shell with touch-sensitive technology beneath, Mighty Mouse allows you to right click without a right button. Capacitive sensors under Mighty Mouse’s seamless top shell detect where your fingers are and predict your clicking intentions, so you don’t need two buttons — just two fingers. Click on the left side to use Mighty Mouse in its simplest, single-button form. Click on the right to access contextual menus within applications and edit, copy, label or download from your mouse. It’s simple sleight of hand.
It Squeezes, Not Squeaks
It wouldn’t be fair to call Mighty Mouse a two-button mouse with one button. Especially when it responds to pressure from your fingers in four different places. Besides the left- and right-click functions, the Scroll Ball clicks down to act as a third mouse button. And force-sensing buttons on either side of Mighty Mouse respond when you press in with your finger and thumb. Perfect for Mac OS X users, the side buttons are pre-programmed to activate Exposé, so you can view all your windows with a squeeze. Of course, you can also customize Mighty Mouse to open whatever you choose — Spotlight, Dashboard or any application when you have Mac OS X v10.4.6 or later.