Gar

Gar has no letter equivalent.

There is no rune poem for Gar. It is a Northumbrian rune.

Gar is the rune mystical unknown, but also of that mystical convergence and meeting place. It is a portal, or door, into the other realms. It opens the way allowing things to pass through to their destination in both directions. While the name of Gar means spear, and so might be a cognate of the Spear of Odhinn, Gungnir, that spear is also the axis mundi, the world center, often described as the World Tree Yggdrasil, whose name means the steed of Ygg, another name of the Allfather.
In essence it points to an open way, an open road, where nothing is set, and every action is a new opportunity. Where it will all lead is in question, because things can change, and what seems fortunate can turn unfortunate, and vice versa.