Resolving unusual actions

[Admiral Squish]

So, it occurs to me, there are some combat maneuvers not covered under the rules.

For example, a tackle. Is it a grapple, a trip, or a bull rush, or all of the above? Is there some mechanic I'm of yet unaware of to express an eye-poke? How about crippling strikes, like targeting the achilles tendon? Or instantly-lethal maneuvers, like snapping someone's neck?

[ArcturusV]

A tackle should probably be an Overrun, a seldom used maneuver. But it fits. Grapple also works, depending on if your tackle is more like the "Knock that WR on his ass when he jumps up to catch the ball" type or "Leave the QB a smear on the ground" type. Various types of strikes can do "Eye Pokes". For example there is a feat called "Falling Star Strike" I believe, which allows you to use an unarmed strike to blind a humanoid or monsterous humanoid opponent. It's basically an Eyepoke with a fancier name. Similarly "cripple" stuff you're likely looking for special class abilities like some Tome of Battle stuff, or feat based things like Stunning Fists, Paralyzing Touch, etc. Snapping a neck is pretty much just a Coup De Grace action, same with slitting a throat, stabbing someone in the lung/heart, etc.

[Sephoris]

Pathfinder has Dirty Trick (http://www.d20pfsrd.com/gamemastering/combat#TOC-Dirty-Trick), a combat maneuver that would cover eye-poking. It basically covers any kind of unconventional combat maneuver that would cause an opponent to be blinded, dazzled, deafened, entangled, shaken, or sickened for a round.