I'd add an example I basically never see discussed about English (in common discussions, it is otherwise very well studied in phonetic linguistics, and mentioned in dictionaries) - weak and strong forms - how sentence stress is indicated by shifting vowels around. For example, the word "the" is pronounced as either ðə or ði, two quite different vowels, depending solely on whether it has topic-level stress ("the question is" vs "this is the question"). Similarly, "a" is either ə or eɪ, again depending on topical stress.

I believe this is quite uncommon in European languages (a system where the same word is pronounced with different sounds based on the topic level stress assigned to it, not on basic prosody/word sequence/etc). Apparently Dutch has a similar system.