I'm down to a couple of pistols, a Webley Tempest in .177, and a Crosman 1377. (with pistol grips and a 1399 stock) I've owned few realistic blow-back CO2 models but honestly, my opinion is that...as cool as they are...the gas used to cycle the action digests too much OF it. Between that, and the temptation to let 'em fly, I find the experience of shooting them very unsatisfying.
My Webley Temptest is one of the British ones (they're made in Turkey now I think) I bought new for $165 maybe 23 years ago or so? To me, the best combination balance, size, power, ease of use, etc. I'll never sell mine, and I don't say that about many things I own!

The 1377 with that stock has really been an amazing gun, got that 31 years ago and have only sent it out for seals 2x. Granted, it doesn't see much use anymore but that gun was a hunter in it's day. I don't think I'd be overly keen using it as a pistol, very much muzzle heavy with that long barrel.
I only have plans to add 1 more air pistol to my collection, and that's a 2240. I had one and like a dummy, sold it. Yes, they're a bit thirsty too in terms of CO2 consumption, but the enjoyment of shooting it far outweighs that factor in my opinion. They go off with quite a thump, are quick to reload, accurate, etc. Balance is very good, they're all business...affordable..and as others have touched on, easy to customize. When I get one again, it may very well stay in it's stock configuration (they NEED nothing) but I may add a steel breech down the road. They're allot of gun for the $ if you ask me.