Film: War of the Worlds (1953)
Location: Civilized area
Height/Weight: The ships are about as big as two tanks. The average Martian is half the size of an average human.
Summary: Mars is named after the Roman God of bloodshed and war. Why should its inhabitants be any different? Indeed, the locals of the red planet are not fans of diplomacy, and would see it fit that we get bumped off the position as dominant species of Earth.
History: Driven by dreams of conquest, the Martians made their mark on Earth feigning a desire for peaceful integration. Alas, when the gloves came off, any sort of defense that the humans might have had proved utterly useless against the invader's war machines.
Notable Kills: Nothing special.
Final Fate: Alas, it is not a weapon of man that downs the Martians, but a weapon of nature. Literally none of the invaders thought that maybe, just maybe, it would be advisable to check for any form of natural diseases that they might encounter. But no, getting sick did them all in. Better luck next time.
Powers/Abilities: Deep breath...GUNS, TANKS, BOMBS!!! THEY'RE LIKE TOYS AGAINST THEM! In other words, electro-magnetic fields render the ships impervious to anything. They are also equipped with an insanely-hot "death ray" that can melt away at the hardest alloy.
Weakness: Anything conventional if outside the ship, though their immune systems also kind of bite.
Scariness Factor: 3.5-Before the diseases showed up, Earth was quite literally at this race's knees. Unfortunately, it doesn't change the fact that the Martians themselves look like a sentient meatloaf with a Simon Says toy for a face.
Trivia: -In 1938, a special radio broadcast for Halloween telling H.G. Well's original story (narrated by Orson Welles no less) was said to cause more than a bit of panic as people thought that an actual alien invasion was taking place.
-Mars is often considered by the top scientists to be a planet that is just as capable of sustaining life as Earth is. The leading evidence is the presence of a biosphere eerily similar to our own.