In Modern Warfare 2, when one would kill themselves with any explosive device (cooked frag, semtex, claymore, flashbang, etc.) when in Last Stand Pro, so as to deny the enemy of a kill.
This move was discovered and stopped in Black Ops, but if you had already planted a claymore you could crawl in front of it and shoot it.
John was knocked into Last Stand but killed the enemy, so he pulled a Sparten so the enemy wouldn't get the points for the kill.
The enemy got lucky and hit Jacob with an RPG, but Jacob crawled in front of his claymore and pulled a Sparten to deny the enemy of the match winning kill.