Masato's got the right idea
Any that is reliable, accurate, easy to use, and powerful enough to kill the target dead.
Before anyone bitches about the scope, it's an early USSR IRNV (Infra-Red Night Vision) scope, that's why it's so bulky.
clearly, the knife
well the Extra Long-Range Bombardment Firearm System for Localized Defensive Use "Harkonnen II" beats it
true, but its kind of situational when you're hunting anything smaller than a zeppelin