So I just started a new fort on top of a volcano. I was at first worried about magma creatures popping up to say "hi" like they had in several other forts I've had so I made sure to quickly put in floors and walls so that nothing bad could get in. However, I didn't completely wall off the magma vent, I had a single obsidian door that I locked and shut tightly so that I could later floor off the rest of the vent.
The next season, I noticed a magma elemental poking around but I didn't want to send my militia since they were all still training and not particularly experienced. Then I noticed the elemental breaking through the locked door (I didn't know they could do that) and attacking the nearest dwarf. It terrified me to think that one of my dwarves would die this early, but when I called the militia to attack I saw how the attacked dwarf immediately changed its sprite to match its speardwarf sprite and began to fight. Before the rest of the militia could arrive, that single speardwarf (with low combat skills) managed to dodge every attack and continually chip away at the elemental with her spear.
She then finished the fight by punching the elemental's face so hard its head flew off. Let me repeat, a dwarf with average strength, agility, and a novice skill level in Striker, decapitated a MAGMA elemental with her fist. Maybe mundane to most everyone else, but that was probably one of the greatest feats awesomeness I've seen a dwarf perform in fortress mode.