Any factory standard ringtone (aside from those designed to be annoying ones). First thing I do when I get new tech is customise every shred of it I can. So, obviously I'm not an Iphone user
I have older friends with phones that aren't of the smartphone variety and they manage to change their ringtone, I guess I just hear the bleating of sheep when a branded ringtone goes off.
That said eventually anything can end up sounding annoying if you hear it often enough!
Bah!! Ringtones shmingtones. My old Nokia says "ring ring" when it gets a call and plays the Nokia tune when it gets a text. I know how to change it but that will do me - life is complicated enough already.