Buddhism

Buddhism is a Dharmatic (i.e. philosophical) religion mostly practiced by the Shi of San Francisco.

Background
Buddhism is based on the beliefs and spiritual teachings of Gautama Buddha (also known as "the Buddha") which focus on how one may achieve enlightenment (Nirvana) through practicing the Noble Eightfold Path. In traditional Buddhism, the Buddha was venerated more as a teacher than a deity, but a shift over time seems to have occurred in the Fallout universe, whereby belief involves the Buddha overseeing the fate of one's soul, presumably to determine if one is worthy of enlightenment.

Additionally, Zen Buddhism survives in the Capital Wasteland with a super mutant named Uncle Leo who emphasizes preaches pacifism and altruism to everyone he meets.

Appearances
Buddhism appears in Fallout 2 and is mentioned in quotes by Uncle Leo in Fallout 3.