working through 4 now and have to vote for that one. 4 includes so many classic elements:

Chandler & Joey peeing on Monica/ 18 page letter to Ross
Selling the entertainment center for a canoe
Joey & chandler getting robbed
The apartment switch (tv genius right there)
Chandler getting handcuffed in Rachel's boss's office
"Pulling a Monica"
the f you hand signal
Chandler in the box
Monica getting a job where every employee hates her/ hiring Joey just to fire him

I still have 16 left to go, I hope the 'PIVOT' episode is in this one.

PIVOT, PIVOT