Bad fullscreen application position after alt + tab
Running some fullscreen application (game), then switching to another window using alt + tab, then alt + tabbing back to the game window causes the game window position to be shifted by the size of the GNOME Shell top panel. Using meta key to open the windows list in Shell Overview and switch to the game window fixes the position. This is how the badly positioned application (in this case Xonotic, but I had the same issue with CS: Global Offensive as well) looks like:
I am using Fedora 29 with gnome-shell-3.30.2-1.fc29.x86_64 on Wayland, but I remember having this issue on Xorg as well.