Paint Shop Pro
I still use Paint Shop Pro 6 at home - which generally still manages to do what I need it to do - which is not a whole lot but still gets there. Fully agree with you that Corel subsequently ruined it.
But the thing that cracks me up (and sort of annoys me at the same time) is that anytime I have to reinstall it on a new machine or VM, the installer blares out some rock guitar music - I guess that was the sexy thing to do with your installers in 1999???