Sarissa was 4-6m long and was used by the Macedonian phalanx.
It was not literally wielded by several people, but ...
The weapons of the first five rows of men all projected beyond the front of the formation..
The sarissas were heavy (~6kg) and unwieldy; I remember reading (back in school) that the sarissas of the rows 2-5 were often supported on the shoulders of the hoplites in the forward rows - this is the extent to which they were "wielded by multiple people".
It is near impossible to "prove a negative" outside of Math, but it is hard to contrive a need for a 2-man pike, as quite eloquently explained by @Steve Bird in a comment:
Two man pikes would double the number of men required in a formation (for the same number of pointy bits)
As for anti-elephant tactics, a simple spear (even a large one) cannot seriously hurt a war elephant, to be of any use it has to be attached to something much heavier than 2 men - Earth or a wagon.
Romans used the following against Pyrrhus's and Carthaginian elephants:
- ox-drawn wagons, equipped with long spikes to wound the elephants
- pots of burning coals to scare elephants
- screening troops who would hurl javelins at the elephants (to harass and panic them)
- disciplined Roman maniples simply made way for the charging elephants to pass (similar to a WW2 anti-tank tactics).