All reality considered, it makes sense that a spear head could be used to slash an opponent, and the shaft be used as a bludgeoning tool. in such a case, couldn't, say a monk, use a spear like a bo staff {incorrectly named the quarterstaff, as this is a method of holding and wielding the staff} as she is proficient is both weapons? Additionally, the head of a spear is usually a short to medium length, thing blade that is normal sharped on both edges, so couldn't that be used in a slashing manner? I am asking, and if so, how would you calculate how the weapon would function.
Many, many GMs will allow you using the spear as a double weapon and let you smack with the blunt end as if it were a quarterstaff. As for the spear as a slashing weapon - no. Look at pictures of spears on google. They are clearly piercing weapons.
You can do this sort of thing using a feat, if that tickles your fancy at all.
Sorry, no link, but I believe Paizo Design Staff have stated that using the butt end of a pole-arm is legit, but would be treated as an improvised weapon (presumably doing Club type damage). In case of reach pole-arms that allows threatening at 5' as opposed to at reach, but they also made clear that you are only wielding one "end" or "mode" at a time, you cannot threaten with both weapons/modes/ends simultaneously.
Paizo has generally ruled rather liberally on switching hands of a weapon, although I'm not sure their rulings on that subject completely cover this case... Which may very well qualify as being treated as "drawing a weapon" since it is in fact a different "weapon" (improvised weapon) vs the "spear" per se.
Think of it this way, most weapons do only one type of damage, those that do more than one normaly don´t doit for free, they either do less damage or have some other drawback to compensate, compared to one damage type weapons.
If you want the spear to do slashing damage or use it as a staff that has reach, there should be some drawback to compensate.
The Monk, specifically, was designed with a limited weapon selection, he doesn´t naturally have access to any reach weapons. For him, to have this flexibility of using a weapons as he wishes would be even more meaningfull than to a Fighter.
In the game world, you can´t use a spear to do slashing damage no more than you can use a sword to smash rocks.
Sorry, no link, but I believe Paizo Design Staff have stated that using the butt end of a pole-arm is legit, but would be treated as an improvised weapon (presumably doing Club type damage).
Can I use my longspear to attack at both 10 feet and 5 feet? I know that the rules for reach weapons don't allow them to attack adjacent foes, but can I use the improvised weapon rules to say that the blunt end of my longspear resembles a club and use it to attack adjacent foes? I know that the improvised weapon rules say they are for objects not designed to be weapons, but the blunt end of my longspear was not designed to be a weapon, right?
You could choose to wield your longspear as an improvised blunt weapon. In this case, it threatens only your adjacent squares, and not the further squares. If you are wielding it as a longspear, though, to threaten the further squares, then your grip precludes the use as an improvised blunt weapon. The rules are silent on how long it would take to shift between the two, but switching between a one-handed and a two-handed grip with a one-handed weapon like a longsword is a free action (and can thus be only taken on your turn), so it should take at least as long as that, thus preventing you from simultaneously threatening all of the squares at once. Incidentally, using the longspear as an improvised weapon in this way would not allow you to benefit from any magical enhancements it may possess, nor would you add benefits that apply when attacking with a longspear (such as Weapon Focus (longspear), but you would apply any benefits from using an improvised weapon (such as Catch Off-Guard).
Well, you could ask your gnome weapon nerd next door. He might build something for you, like this one, based on Weapon Master's Handbook rules:
Starting point
* dmg (M) 1d3
* crit x2
* piercing
* price 1*DP
Decisions
* fighter weapon group: spear
* +6 DP (design points) for exotic
* +3 DP for two-handed
* +3 DP for +45 gold
* -1 DP for piercing or slashing
* -3 DP for crit multiplier x3
* -4 DP for increased damage (1d3->1d4->1d6->1d8->1d10)
* -4 DP for brace and reach
So the result is a two-handed exotic spear, with damage like a halberd, crits, brace and reach like a mundane spear, usable as slashing weapon and a base cost of 57 gold.
While with some weapons as a GM I wouldn't object to modifying the damage ('You want to slice someone with your shortsword and stab with the long? Knock yourself out.'), spears I'd say aren't this versatile in general. If you really want to cut things with a spear, you're probably thinking of a glaive, aren't you?
Now, I'd let it cut something if needed, if we're talking about smallish cuts. Using the head (awkwardly) to cut a string (from far away, of course) isn't really that bad, and feasible with the weapon. Hacking open large wounds in combat? Not as such.
Though this might seem like a relatively harmless request, one would have to think about the implications.
There is already a feat called out by Skreeeeeeeeee that lets you deal different damage type. "weapon versatility"
What if a spear wielding fighter finds himself fighting a skeleton?
Skeletons have DR5/Bludgeoning.
Or what about a zombie?
They have DR5/Slashing.
Both of these creatures immune to the gentle pokes of a spear... unless you had your GM allow you to do otherwise.