Downie 3 is the simplest video downloader It supports more than 750 popular sites such as YouTube (including 4K videos), Vimeo, MetaCafe, iView,and many others. Choose the quality and format of the downloaded file and enjoy your favorite videos.

Features:

Supports many sites – currently supports more than 160 different sites (including YouTube, Vimeo, etc.), and this number is growing rapidly.
Post-processing – do you need your MP4 video for iTunes? Or do you just want a soundtrack? No problem, Downie can’t handle it automatically for you!
Fast support – I respond to emails usually within 24 hours and often add support for requested sites in the next update.
Fast updates – App is updated about once a week with new features, sites, etc.
List of supported services: YouTube, Vimeo, trailers.apple.com, CNBC, NHL, LiveLeak, Insanee, Daily Haha, BlipTV, DotSub, Daily Motion, Over Stream, eHow, Devil Ducky, PlayFM, PBS, Vine.Co, MetaCafe, iView, Bofunk, MadiaSilo, MTV, V-Vids, 15min.lt, Break.com, CollegeHumor, eBaum’s World, ESPN.go.com, NicoVideo.jp, NoiseTrade, On.AOL, Billboard, Cook’s Illustrated, FunnyOrDie, MLB, Bloomberg, Craftsy,Kickstarter, Lynda, NBC News, Rotten Tomatoes, Slashdot, South Park Studios, Video Detective, etc