The tin grenade is an improvised weapon, assembled from scrap items into a thrown explosive device. A tin can is used for both the casing and for shrapnel, pistol powder for the explosive and duct tape to hold it all together.
Compared to a frag grenade, the tin grenade is 20% less damaging and has a 15% smaller blast radius (at 36 feet), but requires no skill to use effectively. It can also be constructed from very common components, so it is arguably more common than any other grenade, especially frags.
PCPlayStation 3Xbox 360 The tin grenade's equip type is 'Mine', so it displays the mine icon within the Pip-Boy hotkey menu instead of the grenade icon.
PCPlayStation 3Xbox 360 Tin grenades are only classified as a standard holdout weapon: they are not added to the list of advanced holdout weapons, so if you have a Sneak skill over 50, you will not be able to bring the weapon into holdout areas. This same bug also affects the Li'l Devil, MFC grenade, and Nuka-grenade.