The M46 Bio-Grenade is an attempt to improve the M45 Fragmentation Grenade. It was immediately canceled for being a danager to human life. It's a very powerful grenade, though. You can rarely find them in Grenade Crates in the place of a M45. It looks exactly like one, except when you throw it by pressing F, there will be tell-tale yellow flashes. Your character will exclaim "M46! Run for it!", and there will be a 25 meter radius explosion in 10 seconds. This explosion does 10000 damage to both zombies and humans.