I don't have a cellphone, but here are ones I would may like if I had one:
- Dies Irae chant theme.... in variants by different composers
- Rite of Spring... especially that dance theme from the opening of 2nd mvt.
- a bunch of people screaming at the top of their lungs
- sound of a crow
- voice saying "don't answer the phone"
- fog horn
- sound of truck backing up
- white, pink, or brown noise
- some very-bangy-gone-into-maddness piano music
- the sound of a phone dialing a number
- a constant very high pitched sine wave
- voice saying "I know cell phone rings in public are anoying, but isn't this ring tone even more anoying?"
- voice saying "What's the most anoying ring tone you ever heard"