four young preppy british guys with a couple of girlfriends caught travelling through the Stares in a London bus whilst on holiday - And one of the girls get irradiated then grows to be....
The 50ft tall British accented girlfriend!!! A 50 foot Billie Piper brings wonderful fantasies to mind.
Native Americans-taking advantage of the chaos to try and claim back their land. - Or, using ancient rituals, CAUSING the chaos to try and claim back their land.
Ancient Native American Shaman's mummy leading other evil spirits from Native American mythos (see above).
Giant anything... ants, spiders, praying mantis, gila monsters, scorpions, snakes, rabbits, etc...
Various alien types... Grays coming to lead an attack on Area 69 to retrieve their stolen ship. Or do probing experiments. Or to grab Earth women for breeding purposes (I heard they're easy). Or to mutilate livestock. Or to make corp circles. Or to take over the world. Or for hunting sport (It sure is growing hot this summer, Billy). Or to lay eggs inside people, watch them pop out, grow real fast and kill everything in sight (and bleed acid blood on everyone).