Basically all point and click adventure games that use the mouse only are perfect for one hand play, because they assume you are playing only with a mouse, so all Sierra/Lucasarts games are good in that regard (actually Indiana Jones and the Atlantis has a fighting minigame, but I'm not sure if it's also controlled by the mouse or you're supposed to use the keyboard as well?).
I haven't played QfG 5 yet, is it possible to map those action keys? If yes, it could be one hand friendly like all the other ones if you can map them to different buttons on the mouse, so you'd have everything controlled by the mouse (as I'm guessing a one handed person would go for one of those 20 buttons on a mouse mouse).
And I agree with Zachovski, the VGA QfG (1, 3, 4) games are supposed to be played with only a mouse, so they're perfect. The battles in EGA 2 are controlled by numpad only, just like in the first EGA version (in the VGA version you can use either the mouse or the numpad).
I actually enjoyed KQ8! But then again, I read a review and knew it was going to be an adventure RPG, so I was really excited about that (and the semi-open world), and loved the puzzles. The get across the river puzzle actually used to be one of my favourite ways to illustrate how point and click adventure games work, since it's so logical and most people probably won't play that game, so it doesn't spoil much. But now I usually just make up something instead.