Leprechaun 2
(1994)

When Cody (Charlie Heath) is attacked by the Leprechaun (Warwick Davis) at the go-kart park, he discovers that as long as he possesses the Leprechaun's gold coin, the Leprechaun can't harm him. He soon heads to the Leprechaun's lair to save Bridget (Shevonne Durkin), armed with a wrought iron rod (wrought iron is another thing that hurts and kills Leprechauns). He goes through much of the Leprechaun's trickery, but the Leprechaun, disguised as Bridget, convinces Cody through a kiss to hand the coin over to him, and once he does he shapeshifts back to his real self and uses his powers to make Cody stab himself with the wrought iron rod.

Both Bridget and the Leprechaun believe him dead, but then Cody springs back up and drives the rod into the Leprechaun's chest. The coin he gave the Leprechaun was actually a milk chocolate coin he got in a pub earlier in the evening. The Leprechaun explodes as Cody and Bridget escape his lair. Outside, Cody tells Bridget that he saw through his illusion because he kisses differently. They then kiss, and Cody tosses the real coin away before they depart for elsewhere.

 Thanks Tornado Dragon!