Command line completion is probably another lesser known one. The command line window is minimized, but typing q: (commands) and q/ or q? (search forward/backward) opens it up completely. Wild mode configures its behaviour.
Video: Holding <Tab> cycles my 666 commands. There's a history limit of 10,000 entries.. Sorry, your browser does not support embedded videos. Here is a link to the video instead. Holding <Tab> cycles my 666 commands. There's a history limit of 10,000 entries. Index: Cache · Source