I'll sometimes have one window from an application that I need to access from all of my Spaces. Often this is a terminal or a specific chat window. Is there anyway I can force the one window to appear on all Spaces without having the entire application?
Edit: Forcing the entire application onto every space is not what I'm looking for. I only want one window of the application.
It's not possible.
There's no preference (even hidden, e.g. through Secrets) for it. Hyperspaces (third party software) does not allow it. And it's exotic enough as requirement (and configuration would be nightmarish anyway) that I'm confident it doesn't exist.
As a workaround, you can move that window with you as you change spaces. SizeUp offers a few related keyboard shortcuts.
At least for Terminal, I suggest using the excellent (free) "Visor" Plug-In that can be found here: http://visor.binaryage.com/ Visor gives you a dashboard-like Terminal window that you can invoke via a shortcut, not depending on which space you are in.
It seems possible through the third party application afloat. See this answer to the same question for details on installation and usage.
