Note that there is still a penalty for spam-clicking - I intentionally never fixed MC-4732 (a very simple fix) because it adds to the consequences (weapons always lose durability when attacking, including during the damage immunity period. This is also not much different from how bows work - they lose durability on use regardless of whether the arrow dealt damage), but it will be less apparent due to no reduction in damage.
I don't normally do this but here is a patched class which disables the penalty (install on top of the original files):
https://www.dropbox.com/s/xju4elgyqntza98/NoCooldown.zip
Note that there is still a penalty for spam-clicking - I intentionally never fixed MC-4732 (a very simple fix) because it adds to the consequences (weapons always lose durability when attacking, including during the damage immunity period. This is also not much different from how bows work - they lose durability on use regardless of whether the arrow dealt damage), but it will be less apparent due to no reduction in damage.
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?