I wouldn't discount revolvers or a 22. Statistically speaking, chances are you'll never use it for home defense(of course chances change dramatically depending on where you live). And a 22 is certainly better than nothing. But you will want to use your gun at the range. A mouse gun in 380 won't get shot much because ammo is expensive, they aren't the most fun to shoot due to recoil(although they aren't as bad as many make them out to be), and they are difficult to shoot accurately. But a 22 is always fun. If the store has one, check out a Ruger Bearcat(I might take some heat for this one). They are quite small, almost kid sized. But they are really cool. I've never actually shot one, but handled them numerous times, and it looks like it would be really fun to shoot. The downside is that it is single action only, meaning you have to pull the hammer back for every shot, but they have a very nice trigger pull. Another option may be the new SP101 in 22. The 22 is a great round to learn with and it will got shot more since ammo is so much cheaper than anything else.
http://www.ruger.com/products/newBearcat/models.html