as per title... Halloween is very close and we all feel the need to add something odd and strange to our homes! I know during this time there are usually lot of games and BatReps with scary themes... and I too chose mine for an incoming game: giant rats!
Big and nasty rats are classic fantasy/rpg monsters, and it is very easy to catch a bag of 10 toys rats and transform them in 28mm wargame models ready for a quick skirmish with your game buddies:
I'm not sure about the rules we'll use. Both Space Hulk (the great 1st edition) and Chain Reaction from THW might be a good choice.