Silicone

Silicone is a popular material for vibrators as well as other sex toys, and for good reasons: It is extraordinarily durable, hypoallergenic, non-pourous, retains body heat and is available in a wide variety of colors.
 Silicone retains its soft, supple feel over time better than most other materials, and it can even be boiled for five to ten minutes, run through the dishwasher or disinfected with antibacterial soap without showing signs of wear.
 Silicone texture can vary from vibrator to vibrator because the manufacturer has complete control over the final product, but they generally choose a firmness level that is soft to the touch yet still somewhat firm.
This is a higher quality material than most, and silicone vibrators are typically more expensive than vibrators made from other materials.