A saccer are players who repeatedly kills themselves in order to create corpses. They are most commonly Necromancers, but anyone with low health, high Illusion Magic, and Illusion of Weakness could also do it. Additionally, Monks carrying a vampiric weapon along with Infuse Health could do it. This build is mostly used in the "Edge Bomb" and "Minion Factory" team builds.
In the Edge Bomb team build, saccers are used in conjunction with Death Nova, Edge of Extinction, and Putrid Explosion. (Note that saccers don't run low health in the Edge Bomb team build.) This team build is less effective since the 17 August, 2006 update, which altered Edge of Extinction to only work on foes with less than 90% health.
In the Minion Factory team build, the saccers kill themselves in order to quickly build up an army of minions. Most Minion Factory teams will work with a Rezmer to speed up the process. Some teams take pets in order to create another corpse and Death Nova bomb.