Check if a strike/shot is available?

[valle2000]

Can a macro be written for e.g. a hunter so it will use Kill shot if it's possible, otherwise an Arcane shot?

[Khatovar]

Macros cannot make decisions for you.

[Fat Tire]

Can a macro be written for e.g. a hunter so it will use Kill shot if it's possible, otherwise an Arcane shot?

There are addons that will tell you when its available. Even if your hunter is not your main. Cooldown pulse is a nice one

[Toned]

If the target is at or bellow 20% health hit your separate macro that has /stopcasting /cast Kill Shot else Mash your dps macro with arcane shot in the click sequence... If you have decent gear / armor pen drop arcane shot anyways it is trash once you get your armor pen up steady is more dps.