Player Configurable Buttons/Keys
Some games (particularly real time strategy and role playing games) provide players a set of buttons in the game's head up display that they can assign to game actions or collections of entities. In some cases, games provide keybindings for these buttons as well.
Strong example Neverwinter Nights [Oster et al., 2002] provides space at the top and bottom of the game view for players to assign hotkeys for skills, spells and items. In addition to indicating which keys are bound to which items or activities, these areas serve as buttons players can click to execute the assigned actions.
Strong example Spellforce: The Order of Dawn [Wertich, 2004] provides a section in the head up display for players to store unit selections. After selecting a group of units, players can assign that selection to a set of buttons at the top of the screen. Stored selections can then be retrieved by pressing the buttons they were assigned to.
Oster, T., Holmes, M., Greig, S., Moar, D., Brockington, M., Knowles, B., Ohlen, J., Bartel, R., and Manthorpe, T. (2002). Neverwinter Nights. Infogrames, windows edition.
Wertich, V. (2004). Spellforce: The Order of Dawn. JoWooD Productions Software AG, windows edition.