Craft Age-Verification Plugin
It allows site administrators to have age-restricted sections on the website, where only adults can enter.
All this happens on a nice looking page which you can customize a lot! (You can even have some custom CSS)
The plugin also features a lot of different ways the user can verify their age:
Drop-Downs? Input Fields? Just some buttons? This plugin has everything.
If you have adult-content, or content that is not intended to be seen by minors, this is probably the best and only plugin on the market right now!