For Ringtones i mostly use songs which have great guitar intros or solos. Im varying often between Dire Straits, Bob Dylan, The Who and stuff. My current one is Walk of Life by Dire Straits.

As for SMS tone i have an 5 or 6 secs clip of breaking glass .
Love to see the reactions of people when riding on the bus und suddenly they hear a window or a bottle breaking.

For Email notif. i didn't know what to pick but i didn't want to use the default either so i now i enjoy the sound of Super Mario Bros. Theme.

I have never liked such ringtones that usually come with a phone.
These midi-style tones that just do weird noises...