The M45 Grenade is a Frag Grenade that appears in SAS: Zombie Assault 4. It is the only version to specify the model number. They can be found randomly in the maps as loot or bought in the shop, and can be thrown by pressing 'F'. They're changed to an upgraded version called the M48 Ultra High Explosive Grenade at Level 30.
- M45: 650 damage, buy 10 for $2000.
- M48 UHE: 2000 damage, buy 10 for $10000.
The grenade is useful when thrown at Shielders, as it can save your gun's clip ammo, as bullets can get blocked; it can also be used as last resort when the odds are overwhelming you. Throwing 2 to 3 grenades at Shielders is enough to kill them, and the rest of your spares should be saved ONLY for these zombies.
However, the grenade becomes worthless if the Shielders or other zombies have Chitinous Hide. Also, it's not worth throwing it for other different purposes, such as throwing it to the bosses, because of the low damage, or blowing up secret entrances.
Note that each grenade only has 10 pierce. If using grenades for crowd control, it is advisable to use multiple of them as one cannot entirely take down a large horde of zombies on its own.
This is a non-combat tip, but you can buy loads of regular grenades before level 30 and sell them once you reach level 30 for a full refund (no profit though). Grenades sell for 20% price, so 10 red grenades sell for $2000, which is how much they cost as regular. As said before, they don't merit any profit, but you don't lose any cash either (besides any you use), so it's good money storage.