Also useful for a "Waiting For" Context, in fact, the default install I believe has a Waiting For Context set to On Hold by default.
Why On Hold? Well, I don't want Waiting For tasks, of which I am waiting for something (email/call/whatever) from someone, to be on my active tasks lists.
However, what I do have is a repeating task (every 2 days), which is to check the Waiting For context (I have a Perspective for this), to see if I have if I need to followup, if I have not heard back. If I do hear back, and the task is back on my plate to complete, I remove the Waiting For context to something else, change the start date (or flag it) based on the priority and my availablity, and bingo, not it shows up on my active lists/perspectives.
And to maintain the traceability (sometimes these tasks go back and forth several times between Waiting For/On Hold and some next action on my part) I use the notes field, and timestamp what I did or what the "delegate" did (this is where TextExpander functionality really shines).
Anyway, the "On Hold" setting for Projects and Contexts in OF is probably one of the most powerful features, and what always seems to bring me back if I try another task management app at times :).