None, Aizen solos dem all.
Wolves are my favorite animals so I have to go with werewolves. Plus, it's a bit harder to kill a werewolf than it is a vampire.
not really a silver bullet and a gun, compared to a stake and your hands. Unless you can find a way to trap a Vampire and keep him/her outside until the sun comes up.
Gun and silver bullet yes. However, one must be able to catch the werewolf first. For vampires, there are more than one way to kill them. First, there is sunlight which is admittedly the more difficult option. Then there is the stake through the heart. This is an easier way to kill since all you have to do is attack the vampire while he sleeps during the day. Plus, you can use holy water, garlic, and a silver cross to repel a vampire. Such things are limited when you talk about a werewolf- silver and wolfsbane are the only 2.
Granted, but the best thing about a gun is you can reach out and touch somebody, if you know that expression, if not, you can kill from a distance(sometimes a greater distance then an eye can see) SILVER SNIPER I think I just made a comic villain lol XD