Paint shop pro version 5.0 (by Jasc). I don't know when it was made but it still sits on my desktop till today and is more useful and handy than any image editing software I've used. It can handle almost all image formats, loads up in less than 1s and everything is so fast and breezy. The Ui is super intuitive that I've never had to once search for help.
Thought I was the only one! :P It's from the late 90s. I myself use PSP6 instead of 5. I don't really remember what the differences were anymore. My only complaint about it is it doesn't do transparent PNGs well (or at all), whether it's reading or writing one. As far as features/functionality/UI though, I like it more than anything else (Photoshop, Gimp, Pixlr on web, etc.). For example, I can never figure out for the life of me how you rectangular-select an area, and just move that area in all those other programs (they always try to move your selection and not the content inside the selection; whereas the default move operation in PSP is to move the content). But then again I'm a dev, not a designer, and I do pretty simple stuff with a graphics program.