Well my favourite coaster of all time is SheiKra. I bet Griffon would top it, but I haven't ridden it. Gutting :-(
But the Inverted I think is probably the best actually. Dive Machine's are awsome, but the inverted coasters are a 'unique' (more unqiue than sit down anyhoo) option, this proving fiarly popular, and the posibilities with them are pretty much endless. Not like Dive Machines where the fovcus is the drop, or the flyers where your limited to hell. Inverters can do so much, and coasters like Montu, Raptor, Black Mamba, and, I suppose, Nemesis, prove this.