-There's quite a few. Try these links. The wiki is good.
http://www.diggerhistory.info/pages-weapons/allied_ww2.htm
http://en.wikipedia.org/wiki/List_of_common_WW2_weapons
-I can only imagine that there are many variations of zombies. There are the different hollywood types, but also cultures all around the world have some version of the undead.
-Not save/load checkpoints, but you can place checkpoints in your map, and if the player dies, they will respawn at the most recent checkpoint ...or something like that.
- You can set patrols quite easily, by laying out waypoints and assigning the approriate script. Making the ai not attack you is also done with scripts. There are premade scripts that do this, and you can also add/enhance them by creating your own.
peace
!