Weddingbee boards

We are trying to figure out which instrumental combination we want for our ceremony music.  Originally we were going to do a string trio or quartet, but it just feels a little too formal for our event.  So we are thinking that a duo might be a better idea.  Does anyone have any recommendations for instrument pairings?  We can have any combination of the following instruments: cello, violin, flute, guitar, piano, bass and maybe others if I ask.  We don't really care for flutes, but has anyone heard good things come from a guitar/cello combo?

I'd definitely suggest an instrument that is played multi-string (like piano or guitar) as one of the instruments.  It will sound much more full that way.  Pretty much all instruments pair well with piano!