A number of creatures in D&D systems (specific editions may not be necessary here, but let's use 3/3.5/3.75 for simplicity) have the ability to use spell or spell-like effects such as Detect Thoughts or Read Thoughts. Dopplegangers are a common case that come to mind. It is said that anyone targeted by these spells get a Will Save. The question is, are they aware of needing to make this save, either before or after it happens, and whether they succeed or fail?
It seems unlikely that the target should be aware if they fail - otherwise, it would deny any amount of discreetness that the mind-reader otherwise has. Perhaps, however, that is the case. What if mind-reading is always intrusive-feeling?
Should a target become aware if and only if they succeed the save? Do they then become entirely aware of what they resisted, or only vaguely aware they "something" attempted to manipulate their mind?
Perhaps the target should never be aware, regardless of if they succeed or fail? Perhaps there is no risk to the mind-reader - only setbacks and inconveniences. Dopplegangers read minds so often that it's unlikely they would be willing to risk even a 5% failure rate.
The 3rd Edition SRD seems to not directly tackle this question, and instead leaves it up to interpretation. What are your thoughts?