I had one in Spanish class a few weeks ago...

I always get sleepy during tests so I usually go to sleep for about 10 minutes. I was "waking up" from this one, and I tried to move but I couldn't. I could open my eyes and see everything, but my entire body was tingling and I heard "voices" (hallucinations~) all around me telling me to wake up. I was freaked out at first because I was hearing people talking but no one was moving their lips. All of a sudden it felt like someone slapped my face twice (once on my forehead and once on my mouth) and then I sort of jolted and woke up.

...it was AWESOME.

I was freaked out at first though b/c back then I didn't know what it was...I thought I was going into some weird kind of trance. (still thought it was awesome though )