A single syllabled word which can mean 'yes' or 'no' or can be used to avoid answering an awkward question. Can be used in conjunction with 'yes' or 'no', or other, to add clarity to the answer you are giving.
Another possible variation is 'heeeeeeh!', simply an elongated version of the original word. This is best used without a conjuctive 'yes' or 'no' and is implemented to shrug off an awkward question, whilst walking away from the person to create absolute ambiguity regarding your answer.
1) "Hey Jeff, can you cover my shift tomorrow night? im heading out with Sally to watch Invasion of the Body Snatchers"
"Heh! I think i won't!"
2) "Hey! Did you pay for that packet of button Mushrooms??"
A response to bon mots or witticisms, not deemed worthy of a full-blown class!