from a few months ago:

i was riding in the the inner lane of dupont circle this morning, in the middle of the lane. as it often is, traffic was pretty much stopped on the outer lane, but the inner was pretty much clear.

as i ride by, a thirtysomething guy in a miata with virginia tags pulls into my lane. he would've hit me sideways if i hadn't swerved and yelled HEY!

i head down 19th street and as i get to the red light on m street he pulls up beside me.

driver (looking embarassed): i'm SO sorry about that, i-

me (interrupting): hey man, it happens to everybody. you'll have an eye out for me next time right?

driver: oh absolutely, i-

me: alright, good talk.

light turns green, i ride away.

not a common exchange, but it's nice when it does happen.