Mwar gave some good choices! Though most of those are rather pricey so it depends on what you are looking to spend too.
My first internal vibrator was the Velvet Touch by Doc Johnson. Under $15 and has some surprisingly rumbly vibrations! I wrote a negative follow-up review but I have since fixed it and love it all over again. I just haven't been able to edit my review.
It really all depends though. Your 4 over all categories would be clitoral vibrators, just internal, rabbit vibes, and g-spot ones.