Cover me! Sweep room! Ruffle my hair! Tie my sodding shoelaces! The beasts from Painkiller - a staunchly straight-up FPS from Polish newbies People Can Fly - would delight in sucking your eyeballs slowly from their sockets if you even contemplated going all team-based on their asses.
Such is the ferocity of the enemy assault, the whole concept of AI almost becomes irrelevant. And before anyone goes off blubbing to Tom Clancy, this is actually not a bad thing. As you're bum-rushed by a constant stream of undead types - mad monks, skeleton soldiers, hells angels, samurais and the like - it's doubtful whether self-preservation would figure anyway. So this is run and gun in the purest sense: Quake before the Quakers started scratching their chins and experimenting. Only even more manic and fun.
Painkiller is about a man going to purgatory and fighting his way back to a peaceful afterlife. Hackneyed perhaps, but it makes for grimly fiendish marauding through cemeteries, swamps, a snowy mountaintop complex and a shapely Venice setting that's anything but Cornetto-sweet. All levels generally rattle with scripted chaos, such as girders falling, fires spreading and runaway explosive barrels.
Oddly, in total contrast some levels are lazy, uneventful and dark. In the asylum, the loons mainly shamble around to be picked off through a mere circle of torchlight. Painkiller's occasional insistence on back-tracking to kill every last freak means such environments quickly get dull.
When Painkiller is on, though, it's on. You want old school without the old hat? Come get it. And bring a spare set of entrails - you'll be needing 'em.