My vote would be for the GSG 1911.22 Its a fun weapon to shoot. Plus it lets me practice my fundamentals cheaply. I have had an interest in a the Walther and the charger. Really I dont think you could go wrong with anything on your list. Just depends what you want to do with it. I carry my GSG around the farm for the woodchucks that always pop up when I am not carrying my rifle.
More than that... but depends on where you get it. Some good prices pop up on the standard model occasionally. Midwest has had some really good prices on them in the past, but transfer and shipping or gas kill the savings from Indy.
Generally you are talking $420 or so locally for the standard model, although as stated I've seen Midwest run them for $379 a time or 2.
I voted 10/22 because they're fun and cheap to shoot and there are a zillion accessories in just about any price range. I love mine.
The Charger just isn't for me but I know people love theirs.
My P22 is a blast to shoot as well but wasn't sure of your objectives and what else you may or may to have. If I were to buy a new 22 semi-auto today, I'd also look at the S&W M&P 22. Only draw back of the Walther is the mag release. I'm pretty sure the new M&P uses the same Walther barrel so you can get the adapter for a suppressor just the same as the P22 but the pistol is a little cooler IMHO.
There was a time when I mocked my friend's 22 caliber stuff but now I find I like mine the most. Just a blast to shoot, cheap fun, great to accessorize, and accurate too.