Wasn't GM1.0 called Animo back then?I've used GM1.0 a bit ironically, but got introduced to it via GM5. Most of my big projects in the past were done in GM6.1, but I transitioned over to GM8 about the time the final Yoyo competition was run and then later to GMS1 for reasons unknown. I'm still too much of a source code management hipster to consider GMS2, but perhaps I'll go straight for GMS3 once that comes out.
I think the first "real" Game Maker version was 1.1.
The oldest version I've used was Game Maker 1.1 (not my first version), very uncomfortable.