Also, interesting trivia. The only character to kiss all other characters was Rachel. [http://www.amazon.com/exec/obidos/tg/feature/-/593794/ref%3Dd%5Fap%5Ffriends%5Fkiss/102-1043328-3000928]
Breakdown:
Ross: Monica, Rachel, Phoebe, Joey
Chandler: Monica, Rachel, Phoebe, Joey
Joey: Rachel, Phoebe, Ross, Chandler
Monica: Rachel, Ross, Chandler
Phoebe: Rachel, Ross, Chandler, Joey
Rachel: Monica, Phoebe, Ross, Chandler, Joey
Monica loses.