DH and I share a cell phone (although I carry it 98% of the time).
When I have the phone the ringtone is currently "Under the Sea" (we go to Disneyland in 6 days
).
When DH has the ringtone I change it to "Bittersweet Symphony" by the Verve (he is a huge Seattle Seahawks fan, and this is one of the songs the team uses).
We have a Virgin Mobile phone, so, alas, we had to pay for our ringtones. But it is worth it to have some personality to our phone.