Leather belt.

Screw on a few more filters to give more area to grip. Gaffer tape the whole lot together, then use a car oil filter or other strap type wrench. Sometimes the hammer is the only way.

+ 1 leather belt

And if that doesn't do it, put the lens in the freezer for a couple of hours. Then use the leather belt. These are tricks I learned in my teens. And believe me, I dropped a lot of cameras and lenses. Only once in my life did I have to cut and bend a filter ring.
;?)

I couldn’t open the link but I am guessing

Use the hammer gently on your finger tips till they are swollen and rough then unscrew the filter
Can’t work out the hacksaw, unless you use this to bite down hard onto when hammering your fingers then a leather belt would be better than a hacksaw.
They say dropping a camera can be very painful.

+1 when you drop a camera. run.

And to work in the other solutions proposed, I think you could use the oil filter wrench around your upper arm in order to really enlarge those hammered fingers.

The gaffer tape I suppose is to use on your mouth after biting down on the hacksaw blade. Don't need to alert the neighbors by your screams that you are so wimpy you can't unscrew a dumb filter.

My CPL always used to get stuck on my lens even though I never screwed it on tight. What I found was that the harder I gripped it with my hand trying to remove it, the harder it got stuck and wouldn't budge. This was because by gripping it hard, it slightly deformed the filter causing it to "bite" harder to the lens thread. If I applied less pressure and used my palm over the front of the filter trying to give even pressure all around the filter edge it came off more easily.

What I am trying to say is make sure you put even pressure all around the filter edge otherwise it will stick harder. After you have tried this, a VERY tiny bit of WD40 (light water repelling oil) between the lens filter and your lens might loosen it up

Another last resort would be to use the hacksaw to cut 2 grooves in the filter on opposite sides then use a metal ruler as a giant screwdriver to twist it off.....

Good luck

"If I applied less pressure and used my palm over the front of the filter trying to give even pressure all around the filter edge it came off more easily."
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I can confirm that this has worked for me in the past as well.

John

wd40 contains solvents that will damage or remove your lens coating if it gets on the surface.
Only thing that "could" be safely cleaned if it accidentally got on the lens surface is a light pure vegetable oil, such as shredder or hair clipper oil.

Rather than a leather belt wouldn't a rubber strap wrench work better?

http://www.amazon.com/Rubber-Strap-Wrench-6-in/dp/B0002H338C

But as others have suggested, adding extra filters (to the stuck one) gives more surface area to grip

Every man in the civilized world over the age of twenty (where pelvis <= gut) wears a leather belt; only plumbers and oil-change specialists carry strap wrenches. I've carried both back in the day, but I always have my belt. Please no plumbers' b*u*t*t jokes . . .
;?)

What about those folks who wear suspenders? ;-) and some "leather" belts are vinyl and may not grip as well.

Yes, if attempted "in the field" you are correct, but if it does not work and you can wait to get home (to your fully stocked toolbox) the rubber strap wrench might work better.

"www.amazon.com/Rubber-Strap-Wrench-6-in/dp/B0002H338C"

You call that a strap wrench? Looks like a dryer belt to me. J

>> and some "leather" belts are vinyl and may not grip as well

Any man caught wearing a vinyl belt should have his man card revoked instantly and be forced to wear pink for the rest of his life. Same goes for a leather tie by the way.

Maybe this is the new embodiment of a guy who really loves his camera... a guy who wears a vinyl belt for his lenses.
It used to be the guy who tripped while filming and heard a crunching sound prayed “oh God please let that be my pelvis.”

After a little stumble and dropped camera, I was left with a wide angle lens screwed in too tightly. The lens was big enough to grasp and permit high torque, but I was worried that the lens mount on the camera may not have been as strong as me :). ( I had seen the effect of another fall with another camera, which broke the lens mount, but surprisingly the camera still worked properly when stuck up with sticky tape!)

I fashioned two boards with a semicircular cutout in an edge, similar to the stocks used for punishment in ye olden days. The "stock" clamp was to grab the lens mount itself, so that there would be no strain between lens mount and camera body proper. I used two woodwork clamps to squeeze the boards together. I then twisted the lens relative to the board clamp with success!

Now here's a manwrench (not recommended for lenses -- or appendages).