FamousRiffs is free app containing more than 150 the most outstanding rock and metal guitar riffs such artists as AC/DC, Metallica, Megadeth, KISS, Judas Priest, Ozzy Osbourne, Scorpions etc. It is perfect for beginner guitarists, because it contains quite simple riffs. Contains guitar riff tabulature and audio, as well as description of the song.
These riffs usually play electric guitar, but they are also not bad sound acoustic guitar.
Each riff have likes and dislikes. You can add riffs to favourites. There are filters for artists and genres.