Here is the challenge: find a word that is pronounced differently depending on its context. I only ask two things: please omit inflections and please omit words with multiple pronunciations that are unaffected by context (words such as route - there exists no situation where it is preferrable to say root over d).

I will take the obvious one first: has.

"He has (hass) to drive to Chicago today." In this case, has rhymes with grass.
"He has (hazz) ten dollars in his pocket." In this case, has rhymes with jazz.

Can you think of any more? I can't.
I suggests "used":

I used [ju:zd] two sheets of paper to write the letter. (p.t. of use)
I was used [ju:st] to speaking fast. (accustomed)

Other words are prepositions with strong and weak forms:

But [b/\t] me no buts!
I called him but he didn't answer. (I cannot find a sign to write the transcription but I hope you know what I mean)
there exists no situation where it is preferrable to say root over d).

except in BrE, where it is the pronunciation of choice. Emotion: smile
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and in this case as well;

i`ve read all the forms(read:as in red)

read the form and fill in the necessary parts(read as in seed)
Although I think it's correct to say dived, many people say dove (long o like cove), and dove (short o, like love), as in the dove (bird) dove (dived) from the sky.