To start off, I would like to make a little confession. I have played this little survival game for almost 250 hours now. Therefore, I feel I am in the position to share a few tips and tricks to make sure you newbies out there have a better fighting chance in the unforgiving and brutish world of Unturned.
If all you have are garden tools, you'd better leave the big zombies alone. They are very fast and take around 25 head shots with a proper rifle. If you can't avoid them, you can try to jump on a high wall in a military base or a container in a city and club the zombie to death, while he can't get to you. I would also advise throwing a smoke grenade so nobody picks you off in the 3 mins you'll spend hacking away at the mega-zombie.