Sometimes when I'm walking down the hallway and I see two co-workers walking towards me, I try to step in front of one of them at the last second and take a charge.  Then I look up at the other person as ask them to make a call. . .half the time they call a charge, and the other half of the time they just sit there wondering what the hell just happened.  Both are appropriate responses. . .

Note:  Do not take a charge on a co-worker that's holding a cup of coffee!