Using the KotS pre-gen characters, and some monsters that I picked up on this site, I put together a little 4e run for three of my friends. At one point, they were fighting a boneshard skeleton which the paladin had marked. The group huddled itself around the boneshard, with the rogue sneak-attacking, and the fighter smacking it around whenever it would attack anyint except itself.
It was almost bloodied, so I decided to have it attack the wizard (who for some reason had strayed into melee range). The paladin was very pleased, thinking that he would get to inflict the radiant damage due to the marking, only to have the skeleton explode, nearly killing the wizard and fighter.
This does raise the question of necromancers making armies of suicide bombing undead. Or, maybe a Lich (who, for some reason heals with necrotic damage) keeping a routine of them as guards/meatshields/healers.