Your favorite one-man band!

I think, whoever the musician might be, one man cannot be a band. I suspect even Paganini who is generally considered the best musician of all times, though not at all the best composer. You need at least two people. The two best duos I heard are Lisa Gerrard/Brendan Perry and John McLaughlin/Paco de Lucia.

I once saw the late great Michael Hedges play "Low Spark of High Healed Boys" on his acoustic guitar. It sounded like several people playing. Todd Rundgren plays all of the instruments on several of his albums Moby has a great time in the studio by himself. Basically, for better or worse, technology allows many artists to perform by themselves and sound like a full band. 

stevie wonder plays everything except guitar on his best records...
skip spence played all the instruments on the outside classic "oar"

Maxnewid,

Funny you should mention Todd Rundgren.  On his record A Capella, every sound is Todd's voice (often electrically manipulated).  It's kind of an ultimate "one man band" in that he needs zero strings (or keys, or anything else).

That album also contains one of IMO the most beatiful ballads of the pop/rock era - "Pretending to Care".  Ironically, the version on A Capella isn't my favorite, but it's certainly an ambitious take on the song.

Jackson Browne. I know he usually has a band, but he did a series of "Solo Acoustic" albums and shows. I saw him, in concert,  twice during this time.

FANTASTIC shows and music!