Generally, the nicotine is what provides the throat hit . . . and the higher the concentration of nicotine, the stronger the throat hit.
Having said that, though, folks have been reporting getting a throat hit with non-nicotine liquids, primarily by adding menthol crystals or drops. Also, some people have been reporting getting a throat hit while using non-nicotine solutions and vaping with high-powered mods.
Also, there is speculation that a warmer vapor increases the throat hit.