I feel really awkward when it's too quiet. Especially at the minute, as I'm really not well with a bad throat and so I can't stop coughing, I feel so guilty for coughing and will keep apologizing for breaking the silence!
Passing someone in the corridor that is an acquaintance and you don't know whether to smile or say "hi" or say nothing at all and you have like a split second to decide. I usually say nothing at all, which is rather rude of me but I'm shy.