Surprised no one has chimed in with All Things Zombie by Two Hour Wargames. Not everyone's cup of tea, but it works for me. (BAM! million dollar rap music career right around the corner.)
You play solo or all players on the same side vs the zombies? Gothcha covered. I've played at a convention with about 20 people around the table, all vs the zombies (at least for a little while, it became a free for all half way in).
You don't have total control of your minis, they may not activate next turn or they may run away when you want them to charge.
The dice mechanics take some getting used to, and is probably what turns most people off. Dice are used 3 or 4 different ways depending on what's happening. After a few small games, it starts getting easy to remember.
There are a bunch of charts, but they are there if you need them. Most of the game is played with only a few charts. The design concept is that the rules are a toolbox, use what you need, leave the rest.
There's a free version so can take it for a spin: link
Get Chain Reaction for modern, or Sword Play for more hack and slash.