My favourite zombie game :D
Firstly, I didn't experience any bugs or glitches in this game like Atomos mentioned. It ran perfectly every time for the 15-20 times I played it. And the gun that Nrenteria was talking about, I think it's called the Barrett or something like that, is missed by a lot of people. It took me 3 or 4 plays to notice that the meter was still filling up after I got the last weapon on the board, which is the AK I think. It also takes a couple of days to find, but it's well worth it.
Anyway... I love this game, and it's easily my favourite zombie-themed game on NG, maybe defense game too. I think the game should be made longer, because 20 days/nights just wasn't long enough for me to fully enjoy the game in one play. If you are to make a second Last Stand, maybe make the game 30-40 days and nights long, and maybe a survival mode or something like that. I think those are the only ways that I can come up with to improve this game, it already gets a 5 and a 10/10 from me :)