I have an old iPhone 3G, that was laying in the closet for a while. I tried turning it on (to give it to someone).
After I plugged in, it showed me the "low battery/charging" picture for a few minutes, then turned into Apple's "booting" logo (see picture). But it won't go past that! It keeps showing that apple logo for days!
If I unplug that it still shows Apple logo, until the battery dies, then if I plug, the picture repeats itself.