Adults
Vampire
Almost everybody remembered the "Twilight" movies being released back in 2008. Since then, so many people have been hyping up vampires and making them look "better" than their Dracula and Nosferatu counterparts. Making them look more "normal" like a human, slightly pale, and (for some odd reason) more good looking; thanks a lot, Robert Pattinson.
Witch
Surprisingly, the most common adult costume (primarily for women) is the witch. But at the same time, it doesn't come as a shock to some since it is easy to make, given that it can be straightforward to make. Others prefer going a different route and making the witch costume more elaborate. Some might even make it more erotic (wink wink) for some Halloween parties.
Ghost
What can we say about this one… put on a white bed sheet, poke two holes for your eyes, and boom, you have a ghost. Honestly, nothing much to say here. Boo!