I'm actually surprised people still customize ringtones. Every time I hear a ring on someone else's phone it's either just a vibrating hum from Silent modes or whatever that OS/brand's default ringtone is.
edit: I do customize my alarm tone though as the default tones are too mellow to wake me up. For that, specifically, it varied as an assortment of 1. metal and rock songs, 2. Adventure Time characters shouting, and 3. Edith Piaf's Non, Je Ne Regrette Rien because of Inception.