Blood splatter. One of my all time favorites but also one the messiest.
Crackle polish in Halloween colors like Julep's Sabrina.
Patterned nails like these candy corn nail stickers from Sally Hansen.
Ghost nails and/or candy corn ombre. Simple yet festive.
Or if you're not brave enough to attempt nail art then perhaps try KISS imPRESS Press-On nails for $5 at your local drugstore. These "Treasure Island" nails are super cute but they come in a variety of Halloween styles.
How are you painting your nails for Halloween?