The Cello

... is, according to Wikipedia, "the second largest bowed stringed instrument in the orchestra" (my italics). The harp is a stringed instrument, and it's arguably bigger than a cello. I can't think of any other examples right now, but ...

Also ... should we not accept "violoncello" as an alternative answer? I can remember when 'cello was an abbreviation for violoncello - but Wikipedia doesn't seem to recognise this, so I'm happy to accept that it's now called a cello - but violoncello is an alternative name.