Oh olfactory hallucinations! I once had one maybe?

I was driving home in very bad (snowy) weather, and all of a sudden the car seemed to fill up with sandalwood incense. It felt very portentous. And then it faded. And then when I did finally make it home, I found out that Waka had been burning incense. Oooh, twilight zone.

As for other sorts of hallucinations, I have had visual ones on the verge of sleep, things I think I see, and then I look again, and they're not there. My kids have had the auditory ones--they'll be relieved to hear they're normal.