This doesn't necessarily qualify as different - but my wife and I did it last year and had a good time:

Do a walking tour of the city - because SF is so compact you can hit so many of the highlights on foot.

Start out near SBC Pack and head out toward the Embarcadero. Walk along the bay stopping at some of the more interesting piers and certainly the Ferry Building. You could also hit the Equinox atop the Hyatt across the street from the Ferry Building on Market. Eventually you'll get to Pier 39, Fisherman’s Warf area.

Toward the end of the "tourist" area of the Warf you can cut up and head back across town - I forget the exact street but you'll be able to walk through the North Beach area (lots of great Italian places to eat), through China Town and you'll end of in the financial district. From there it's about a 15 - 20 minute walk back to your starting location, and if you time it right you can then catch a game at SBC Park.

Plan on 3-4 hours minimum, add appropriate time if you stop to eat, etc. You won't see anything that unique or different, but you'll experience SF on foot and that is quite fun.

Bruce