Last year I presented myself with Daisy 499 - an advanced version of Red Ryder. Much more accurate and much less powerful than Daisy 880 that I bought earlier (an impulse decision, but hey - I was dreaming about it for 40 years and it was on sale for $35 :).
Did a research before buying it, CO2 didn't fit the bill (and you can't fill cartridges yourself), stopped on BB as an extremely cheap alternative (BB shot is ~$0.001, .177 pellet ~$0.01, .22 real rifle 8c-10c, and 50 shots on a pump rifle like Daisy 880 is at least 30mins of pumping fun).
I'm really happy with Daisy 499 - you won't hurt a squirrel from 10 yards, but you'll annoy it by hitting it every time you shoot. And it's a perfect indoor shooter, which is a huge pro here in Seattle. Just remember to wear safety glasses, it ricochets ALOT when you plinking instead of doing paper targets, but safety glasses should be a must for every BB gun.