Months back I did a post on Youtube covers of the Pokémon theme song that I love and, while I still love all of them (well, most of them minus the last one), I recently came across a cover that totally outstrips in terms of technical proficiency and overall impressive effort.
This dude? He did the entire song, backing track and instrumentation and all, by himself, a cappella. Meaning he was every single instrument in the song. The faces he makes are kinda distracting but the overall effect of the multiple parts is really impressive.