Garlic

Garlic is an item used for the Fishing Contest, Desert Treasure, and Vampyre Slayer quests. It is also need to make Guthix Balance for the Morytania Medium Task. Despite being a food, it cannot be eaten on its own. It is used, though, in making Spicy sauce and Guthix balance potions.

Garlic may also be used along with a stake and a hammer to kill Count Draynor, a level 37 Vampyre, at the end of the Vampyre Slayer quest.

Members may grind garlic into garlic powder with a pestle and mortar.

Garlic can be found at these locations:

Respawns on a table in a house in Seers' Village.
Bought or thieved from the Spice seller in East Ardougne.
Respawns on the Red table of the cooking range house, near East Ardougne; located west side of Town square.
Can be found in the drawer in Morgan's house, located upstairs in Draynor Village.
Bought or thieved from Greengrocer vegetable stall in Etceteria and Miscellania.
Traded at the Grand Exchange.
Can be found in a Teak larder of a Player-owned house
Can be bought from Wydin.

Trivia

Before the release of Nomad's Requiem, the examine text for garlic was 'Can be found lying around Draynor Village and Ardougne'. This text was only used for help on where to find it, but was unreasonable as garlic can be obtained in several other places, and could only be examined once the player had already found one.
Even if your membership has expired you can still grind garlic into garlic powder, assuming you have a pestle and mortar in your toolbelt, even though it becomes a 'Members object'.