The Adafruit Silicone Elastomer 4 x 4 Button Keypad is a little different from most microcontroller keyboards, instead of hard plastic buttons, these are squishy elastomer. Each button has room for a 3mm LED so that you can illuminate just those keys that are active in your project. You don't have to add LEDs, but it does look pretty cool; diffused LEDs are the best. Because they're made from soft silicon, they're washable and you can trim off any buttons you don't want. Adafruit have also made the keypads edge to edge tileable to create larger arrangements. Each button has a conductive ring which makes contact with a properly designed PCB underneath (not supplied). Adafruit provide an EagleCad library so that you can design your own. Alternatively you can pick up an Adafruit Trellis driver PCB which will do it for you.
4 x 4 button matrix with room for 3mm LEDs in each button
