"A special item that Regina brought herself."
Inf. Grenades (Infinite Grenades) are an alternative ammo type for the Grenade Gun.
They are an infinite ammo version of Grenade Bullets. As their normal conterparts, the bullets explode on contact and deal a high amount of damage. As their ammo are infinite, they should be used on all non-mobile opponents, including all types of Velociraptors, Therizinosaurus and Tyrannosaurus.
It can only be acquired by beating the game at least 3 times and seeing all the 3 different endings, thus making it appear in the inventory along with Grenade Gun at the start of the next game after seeing the last distinctive ending.