Hmm, Gligar and Gliscor is an interesting one... But I personally like their typing as it is ^^ I think the Flying/Ground typing defines it more than a Flying/Poison or Ground/Poison typing would. :3 Plus it doesn't learn many Poison moves from memory? I think Sandshrew could do with a Poison typing, especially considering some of its staple moves include Poison Jab :3 New topic!
New topic: 'Which Poison type do you find scariest?'
I think Drapion!