Was working in Douala, Cameroon in June and got shook down by the local constabulary.
A van pulled up as I walking down the main street, the door opened and I was immediately followed by two men. They quickly hailed me and stood on opposite sides of me.
The main guy claimed he was an undercover policeman and needed to check to see if I was in the country legally. I aksed to see his identification and he showed me his handcuffs and an ID card that looked about 40 years old and might have been my grandmother's library card.
He asked for my passport and asked if I spoke French. I speak fluent French but played my role as a "stupid American" and claimed I did not. I had my passport in my pocket but claimed that I had left it back at my client's office.
I offered to walk with him to the office so he could look at it but he refused. he offered to give me a ride which I politely refused (as this seemed SCARY AS HELL).
As time passed and I wasn't cooperating and wasn't about to give him any money to go away he did let me make a phone call from a local merchants shop. Needless to say, one quick phone call to my large, multinational client and they immediately sent over their security personnel over to rescue me.
The cop actually followed us to the office and was eventually allowed to look at my passport. I coudn't believe the nerve of the guy -- he still expected he'd get some cash. All he got was a tongue-lashing from the managing director.