By "sudden", I mean that there is no dedicated harmonic preparation leading into the new key.
The commonly used ones I can think of are:
- Up a semitone (the classic signal that this is final repeat of the chorus before the fade-out in a pop or rock song): E->F
- Make the dominant the new tonic: C->G
- Make the subdominant the new tonic: E->A
- Down a semitone (much less common than up a semitone): C->B
What other intervals between keys are often used for sudden and surprise key changes?