That's a really great question!
For me it has to be the reconstructive nature of memory in Loftus and Palmer's research. For me there's nothing more piquant about psychology then in understanding how and why our minds can fool us.
So the fragility of memory and how false memories can easily be implanted through verbal communication is fascinating.
Other generalised research such as Milgram's obedience studies intrigue me just as much, but what I love about Loftus and Palmer's research is how it has led to a revolution in interview techniques.
What about you do you have any favourite research, or research that interests you most?