As previously discussed in the secrets thread, punch walls exist in levels 2 and 4.

Max has access to about a dozen, all of which seem to function the same.

Kurt has access to 2. One has a 100% chance of dealing a punch, and the other is normal.

Normal punch walls have a 50% chance of dealing a punch, and a 50% chance of dealing an item. Intrestingly, the old Interplay official walkthrough stated that there was a "2% chance" of getting a unique super weapon that could only be obtained from the punch wall. I have spent enough time with these that I can confirm that they do not exist for the PC version of the game. However, there were some interesting things I found:

Max
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Common
---------------------------------
AA Battery
Magnum
Uzi

Uncommon
----------------------------------
Shotgun
Car Battery

Rare
-----------------------------------
Double-items (any 2 of the above)
Triple-items (any 3 of the above)
Quadruple items (usually AA battery + Uzi + Uzi + Magnum)


Kurt
=====================================

Common
------------------------
Grenade
Sniper Grenade
Super Chaingun
Orange

Uncommon
------------------------
Homing sniper shell
Sniper mortar
Dummy Decoy
Ham

Rare
-----------------------
Cloak


As a geneal rule, it looks like there is no way to get a weapon that cannot be found in the level. This means no miniguns, rayguns, etc. Also, since Kurt can "stack" items with no limit, I had him armed with roughly 800 grenades, 1,000,000 rounds for the super chain gun, 1500 sniper grenades, 5 cloaks, and 25 dummy decoys when he went to face off against the boss.

Has anyone played around with these on different systems?

Hey there sirbobbington! Nice to see another member of Hectic HQ!

I mostly avoid the punch walls, but sometimes you may find it useful - for example, when you want to heal yourself. Of course you can also lose more of your life points. It's like Russian roulette.

Thanks for sharing your insights. Our little community needs more of such topics

@ sirbobbington: Actually I dont get how could you manage to collect such amount of stuff when there wasnt so much items in single level and after finishing a level you lost all unused items you had left. So the only way you could gather such amount of stuff is cheating.