Occasionally an NL team bats a pitcher 8th if their leadoff hitter has a bit of power. The logic being that it makes more sense to hit a guy 9th who has a better chance of getting on base to be moved over by the leadoff guy when the order cycles around. Makes a bit of sense to me.
On the flip side, batting your pitcher 8th just gives him a better chance of killing a rally if the 5-7 hitters are on base.