You-Get - Command-line utility to download media contents from the web
CONV. - Convert YouTube video to MP3, GIF or MP4
YouTubeDLD - World's most efficient YouTube downloader. No spam or ads.
Downie - Video download for OS X. Downie supports at this moment over 1,000 different sites.
Every Second - Realtime stats per second of Apple and YouTube
Yout - YouTube to Mp3 Converter