Cleric: the backup for the "meat shields." Healing is needed afterwards and the other magical powers are usefull, too. And I can always try to find new followers for my religion.
Back in the day, one of the more common professions I saw was Channeling Healers who wanted lots of ranks in tumbling (Attack/Evasion) and MA Grappling,
in hopes they wouldn't have to wait for afterwards. Pull the guy out
from under the middle of the melee, transfer, and send him back in.
Sometimes they even got away with it, but it's not for the faint hearted. Then again, Healers can afford to be suicidally courageous, since they're nearly impossible to kill without having to stop and think about it, random blows mostly won't do the job.
"Did you see those Huns? They just popped up out of the snow! Like daisies!" - Mushu
The other professions I most commonly saw were Rogue, just for the versatility, and some kind of semi spellcaster, usually a Ranger or Warrior Mage. The again, my players were usually half a dozen or so people who were more than a full day's travel from the nearest town (or even village), so they tended to try to cover everything. If the meat shield is down,
someone has to be able to step up long enough for the Healer to get him back on his feet.