On occasion, I will hear ま being used in a way that seems to suggest the speaker is responding to something indignantly. Something like, "Well! If that's how you're going to act..." Are there any good examples of how intonation can change the perceived meaning of ま (when used in isolation)?
There is no word ま that matches your description. The interjection you hear is probably まあ or まっ. It expresses a surprise rather than indignant tone.
There is also まあ/まっ which is a filler (and sometimes compensates a potentially bad situation), something like the English "well".