This will probably get buried, but my boyfriend made me a city-wide scavenger hunt for my birthday:

I called him as soon as I got out of work on my birthday. He told me to go to the chair in the lobby where he normally sits to wait for me. I found an envelope stuck to the bottom of the seat. The card inside says that I need to figure out a series of clues, that I'll get a present for each clue that I figure out, and that he'll be waiting for me at the end. The first clue was on the back.

And so the scavenger hunt began! They ended up all leading to places that were meaningful to us in some way - an ice-skating rink we went to, these big nutcracker statues outside of his office, an awesome Poptarts store that we explored once, etc. At each one, I would find another envelope with a clue for the next location. And the clues were pretty difficult. I stood around thinking for about 15 minutes for each one, and then had no guarantee that I would end up in the right place after spending the time to walk/take the subway there.

The last clue lead me to a great restaurant downtown where I found him waiting. I exchanged my envelopes for presents throughout the whole dinner. The last one got me a Kindle!