Depends on the situation.
If I've been sneaky and managed to gain an undetected aerial advantage on my foe, then I'd take the tyre. Drop that bastard on someones head and they won't be getting up in a hurry.
If, however, my cover has been blown and I am face-to-face with my would-be assailant, then I'd choose the cows hoof, as it looks like it could be an effective bludgeoning tool. Having said that though, I'd probably run away.
I'd take a tyre, they are well heavy and could do some real damage. If you like you can imagine that your opponent has the weapon that you don't choose.
Well with the tyre you'd probably only get one throw which would be a bit slow and sluggish and they'd see it coming from Polegate anyway so prolly duck out of the way in time.
Is it allowed to have the car tyre still attached to a Range Rover? Or the hoof still part of the cow for that matter?
It could sway the decision.
A mightily upset cow kicking away could do some serious damage in a confined space. But then again the Range Rover would be good for buggering off sharpish if things start going badly.
You can chuck it at your assailant, when it goes over their head it will secure their arms in place leaving your free to batter and kick at your pleasure!
"Pointed stick? Oh, oh, oh. We want to learn how to defend ourselves against pointed sticks, do we? Getting all high and mighty, eh? Fresh fruit not good enough for you eh? Well I'll tell you something my lad. When you're walking home tonight and some great homicidal maniac comes after you with a bunch of loganberries, don't come crying to me! Now, the passion fruit. When your assailant lunges at you with a passion fruit..."