Mimic and mental powers

[Ganondorf]

Since you clarified that you mean things that are harder to perceive... here's the quick and dirty answer: If you can't perceive it in some manner, you can't copy it. If you have an ability which would allow you to perceive it (such as Insight), you're good to go. OR, alternatively, if you witness someone use an ability which has a way of being "seen" (such as Regeneration), or if someone explains to you how it works.