Programmer's Notepad is amazing, its been my goto in Windows for well over a decade at this point. Has everything I need without any bloat, also work fine on large files (I often do regex-searches on huge log files with it).
It was definitely xkill, I remember using it a lot during the early Ubuntu releases. I think the shortcut was ctrl-alt-esc, but its so long ago it was removed I no longer know for sure.