This actually happened last night.
Me and my friend were walking home from a party, and we passed a generally abandoned campground. We heard a dog barking, which was unusual since it was one in the morning. The bark sounded weird though. It kept persisting, until we both realized what it actually was. It was a guy imitating a dog’s bark. We heard insanely aggressive crunches coming from the woods, so we booked it back to my friends house.
Maybe not the creepiest thing ever, but it really freaked us out.