The lasso seems really cool, but I'm not really finding it effective against the zombies. Since they always move towards you, it's easy to get them into a group and kill them all with one grenade, without using the lasso at all. Also, as far as I can tell you need one grenade per wave in order to kill the zombies, but when I got to wave 3 I didn't get a grenade and thus couldn't progress any further.