I put the / between horror and action, so that it'd broaden the amount of movies in it. Besides, many horror movies tend to have action in them too, and are more action than horror, actually. I put modern in brackets because it's more common to have action/horror from 90's and onward. I don't really know any action/horror movies before the 90's... Jaws (maybe)?
Anyway, mine's shared between all the Underworld-movies and Blade-movies. If I had to choose I'd select Underworld ones before Blade, though.
I've found them to be pretty awesome. It's also an example of movies that have characters more commonly connected to horror movies (vampires, werewolves), but are actually more about action in these movies (franchises).