A few things to consider:
As someone else said, *most* municipalities consider airguns to be firearms. Depending on local incidents (ie, kids shooting out streetlights, and at people passing by) they may or may not enforce that around there.
If you're going to be shooting indoors, you will definitely want a pellet and not a bb gun. You will also want to buy or construct a proper trap for them, because even pellets will ricochet (we used to shoot at the driveway at just the right angle to make that sound they always make in old westerns). A .22 pellet gun is probably going to be more power than you want for indoors. It shouldn't, however, be hard to find them or ammunition - WalMart and local gun stores usually carry it (unless WalMart changed things since the last time I happened to get airgun supplies, which was admittedly a while ago).
It's hard to recommend a gun for indoor use - I always bought them based on power and reliability. Only the cheapies are really indoor guns, like that .45 that shoots darts, bb's, and pellets. I can tell you that I own five different airguns, all Crossman.
1377 - original gun, back when it was more metal than plastic. Pump action pistol.
Powerline .45 - I'd avoid this one. It's a pain to load, the trigger was always very heavy on every one I ever pulled, and it's CO2.
.357 - great pellet pistol, three different barrels available, six or twelve round clips, downside CO2. And don't EVER fire bbs in this thing, cuz they fit and work until after a couple of hundred rounds when one gets jammed and completely screws up the barrel
powerline 1200? - it's a grey stock rifle, twelve round clip held in a false magazine (one of the more realistic looking air guns), again downside is that it's CO2 (goes in below the barrel)
Then there was this pump rifle that I don't remember the number of. Great all around rifle though (and it wasn't the 880).
I guess my best recommendation would be for a pump - you can control the power then, whereas with co2 you can't (plus you have to buy them cartidges). A .177 is more common to find supplies for than a .22, and usually slightly lower FPS ratings. In my experience, Daisy tends to be cheaply constructed, Crossman much better. There there's all the smaller companies who may practically be gunsmiths or might be Red Ryder clones.
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