The Legend of the Five Rings collectible card game once included the terrain card "Come One At A Time," which allowed a single samurai to hold up (and, more often than not, completely destroy) an entire enemy army by invoking this trope.
L5R has also invoked this trope multiple times in its storyline. Notable instances of You Shall Not Pass include the death of the Kami Akodo, and the Battle of the Land Bridge.
Magic: The Gathering, in its Kamigawa block, has a card named Hold the Line, which gives absurd bonuses (+ 7/+ 7) to all blocking creatures for fairly cheap. The flavor text, though, is supremely awesome, especially in context:
Forgive me, Master Kami, but in the interest of my people I must halt your advance.
Similarly, the spell Righteousness gives + 7/+ 7 to a blocking creature for one white mana. (For comparison, the closest thing green, the color of big fat creatures and big fat creature effects, has to Righteousness for the same cost is Giant Growth, which gives only + 3/+ 3 to any creature—but Giant Growth's target doesn't have to be a blocker.) There is also the "cantrip" spell Gallantry and the much-less-impressive but thematically-similar Rally.
Two more spells—also white (noticing a pattern?)—give a single creature the ability to block any number of creatures in combat until end of turn: Blaze of Glory and Valor Made Real. Blaze of Glory has the sort-of downside of requiring said creature to block every creature it can, though that doesn't prevent other creatures from helping out. Finally, the Avatar of Hope may block any number of creatures as an innate ability, and if you are in dire enough straits can be played for minimal cost. There are other white spells and creatures with similar powers, but they don't have the flavor of these ones.
Blaze of Glory's downside can be turned into an advantage if cast on a creature with deathtouch and that has had Righteousness cast on it at the same time.
As long as Hundred-Handed One is monstrous, it has reach and can block an additional ninety-nine creatures each combat.
The Yu-Gi-Oh! card game has a few cards like this—My Body as a Shield requires a payment of 1500 Life Points to protect creatures from destruction effects, and the special power of Stardust Dragon does the same thing, substituting the Life Point payment for the dragon's own destruction.