Let me introduce what I think is a damn fine paint stripper for wargamers, it's called dettol and it's an all purpose disinfectant. Now I've heard a lot about simple green but I'm damned if I can find any of it, I've also heard that fairy power spray is good for stripping models. To be honest, I couldn't tell you how good either of them are, and I'm probably not going to be able to tell you about them in the future because I'm sticking with Dettol from here on in.
It's really simply to use, just drop your models (metal or plastic - don't ask me about finecast, I don't buy that stuff!) into a suitable container like a drinks beaker and then pour in enough Dettol to cover them. Give them a swirl with an old tooth brush.
I left those metal snipers I got from eBay in for about two hours and after a quick scrub with an old toothbrush and then rinse it in water. 99% of the thickly applied paint came off in a matter of a minute's scrubbing and it's ready to be primed again.
A quick word of warning, I'm not going to say that Dettol doesn't damage plastic because it does. I put some SDE Kobold warriors in to strip after my wife had tried painting them and then I completely forgot about them. A week later, I pulled them out to find that the paint had stripped and the hard plastic model was perfectly fine but the model base which was made from softer plastic had melted as you can see in the pic.
So obviously over time Dettol does damage plastic but considering they'd been in a week and they only needed to be in for an hour, personally I don't see this as a problem, just something to watch out for.
Finally, another quick word of warning, Dettol seems to make the paint like a sticky tar substance which cleans off easily with Dettol but not soap and water. So make sure you wear gloves when handling them models and do it on a surface that's easy to clean gents!
Anyway, I'm off to strip some more models now I know how to!
Mel
EDIT - From the comments. Here's a list of other blog posts that cover different paint stripping fluids ...
If you've got a good relevant post, let me know in the comments and I'll get it added guys.