If an electronic device exists, it has a Youtube app. If it does not, it will soon. The Nintendo 3DS can now be moved into the former category, as the YouTube app is now available in the North American and European 3DS eShop. Check out the below video from YouTube user HashtagIdiotic to see the YouTube app in action.
YouTube App Now Available on Nintendo 3DS eShop - News
By Brent Galietti, December 1, 2013