What kind of action is it to give and take a weapon during combat?
Can two characters have a single spear between them, and pass it back and forth, such that they can hold their ground and make standard action attacks?
There's no actual rule for what kind of action it is that I can find. I'd personally make it a move action that might provoke an Attack of Opportunity.
If you want a 100% by RAW way of doing it, it's a free action for the guy holding the spear to drop it and the other guy can pick it up with a move action (this is part of my reasoning for how I'd do it above).
We usually say it's a free action for the giver and a move action for the taker. There are some situations that have to be taken into account sometimes (like positioning, attacks of opportunity, etc.)
so what you are trying to do is having two people fight with the same weapon in the same 6 second time frame, back and forth?
As GM I'd so NO.
IF you wanted to I dunno have on guy attack one round and the other guy attack the other round, while the unarmed guy was casting a spell or doing something else, it MIGHT work... but it's still really weird.
Ah, I missed that. I would not allow two characters to use the same weapon in combat in the same round. The concept of the game round is that it's all happening at once. The initiative order and turn taking is an arbitrary concession to this being a game with players who have to roll dice and move stuff.
This kind of thinking is what leads to the construction of peasant rail guns.
I would rule it is a move action for both characters. It takes some coordination to perform this. It is surely more difficult than just letting go.
I would allow them both to use it in one round, once. I see nothing wrong with handing over a weapon to let another use it. I would cry foul as the DM if they kept trying to go back and forth but making it a move action would limit it anyway.
Here's a related fighter class, I just came across.