I wonder how many arms and heads that a lot of us would need if we counted singing and every instrument that we are cable of playing a simple melody on (lets say the melody line to the Wild Rover). I would have to remind my self on some instruments which I haven't touched for a long while but my own list would include:

Tenor banjo, 5 string banjo, ukelele, guitar (6 string, 12 string and bass), mandolin, mandola, bazouki, cittern, piano, fiddle & viola (very scratchy bow but in tune), whistle, recorder, clarinet, appalacian dulcimer, hammer dulcimer, harmonica, piano accordian, GD melodeon, anglo concertina, harp...

Additionally of course everybody can "play" the bodhran (no offense meant to those who genuinely do play this instrument - I love it in skilled hands).

Jon