These are my choices and I own at least one example of each.

1)CO2

Crosman 451 - well engineered and the first blowback pellet pistol.
Crosman 600 - well engineered terrific fun multi shot pellet pistol.
Crosman Mk1 - well engineered plinker/target pistol.
Makarov Gen1 (1999) feels like the real thing.

2) Springer

Webley Premier "A" series. In my opinion what the much praised Senior should have been (indeed became) - easier to cock with a much better trigger.
Webley Tempest, Typhoon and Hurricane - terrific fun and you need the full set.

3)Ram

Webley Nemesis - underrated, smooth shooting and cheap for what it is
Webley Alecto - (had to get one to complete my Webley collection (I know it is not a proper one).

Finally I am the only person I know who does not rate the HW45. I had one and found it too clumsy and, dare I say so, boring to use.