How many planet do we have? Eight..

Pluto has been redefined not as a true planet anymore, it's now classified as Dwarf Planet. So now, you might find Gimli there :). So if you're being asked in exam how many planet we have, you have to answer EIGHT. But there is a possibility another planet will be defined in the future. No one know exactly what things are in the universe.
Source: http://en.wikipedia.org/wiki/Pluto