Note-taking: It seems to me that many games that would benefit from it don't allow the player a way to make notes of important information that they may wish to remember, which means you must use Notepad or something (or a real notepad), requiring extra effort. Some roguelikes have a way to add a note to the log, and I think I know of at least one that will let you see a list of all the notes you've made (either DCSS or ToME, maybe). So, either add it to the log and have a way to call it up, or use a special window.
Location labels/markers: Locations the player considers significant can be displayed on the map (displayed and hidden via intel panel). Maybe also allow a short text input that could display upon mousing over the icon. This text could also be added to the log:
Location marker created.
Location marker created with text: "1,000 Pests - stay away!"
Unit labels:So, when a labeled unit comes into view, it will flash a special color or symbol or have a glow or scan effect around it for a moment. A slight glow or flashing icon could follow them as they moved around, so you could tell them out of a crowd. Text could be useful for this, too:
Identity memorized.
Identity memorized with text: "The hauler that took me legs!"
This would reduce the need for players to manually check the ID of robots to find a specific one, if that feature is implemented. Possibly terminals could also create some labels, if this creates any good development ideas.