Hiccup is a good inventor/contructor of things, many of which have weapons-like qualities. Of course, his technology is steam-punk level, minus the steam, but he is really very good at it.

He also has this dragon: the dragon can fly super fast, take off straight up in the air and fly incredibly high, shoot super hot balls of flame, and has sharp teeth. The dragon may also be capable of cute-ing people to death, but that's yet to be tested.