#3 or #5. I don't know how any of the others could be justified. I don't think it matters whether it's got $1, $1000, or $1000000 in it, except in the latter case I'd probably take extra security measures and demand a receipt from the police when I turned it in.

I found a wallet a couple of years ago. It had what looked like a decent chunk of cash in it, but I didn't look to see if it was 1s or 100s, since it didn't matter. I dug out the driver's license so I could return it, and it was from 200 miles away so I actually dropped it by the police station on my way by.

For everyone's info, it turns out that you can actually drop found items in a mailbox; it's actually one of the post office's charter functions to return lost items to their owners. I'm sure they appreciate only dropping things of some value in there though.

I've also returned a couple of cell phones, most recently to a high school student who apparently had it stolen from his locker during gym class, and it had been thrown out a car window. Just had a scratch and a little mud on it.