O_O Quite a weird thread, but I think there is a clear winner here, though it is a really unfair question. I'll start with the best physical wall...no, best OVERALL wall.
Skarmory.
Skarmory has an astounding 140 base Defense, so obviously it can take most any physical attack. But one of its greatest assets is the ability to set up spikes and the roar at the opponenet to annoy them immensely. And the cool part is that since it fears madneton/magnezone, there are ways in each gen to destroy it. In both 3rd and 4th gen, you can set up a sub and roar it away while it breaks your sub. In strictly 3rd gen, I found it fun to run a Choice set with HP Ground to OHKO the little magnet. And 4th gen, shed shell allows you to escape :0
As for its walling capabilities, it can wall about any physical attack. You might think that its base Def helps so much, but that isn't the key. Think about it like this...skarmory has a trcukload of resistances. It freely switches into earthquake and other commion physical attacks. Resists normal types as well. The only annoying physical attacks that could inflict harm were choice banded focus punches and rock slides from the likes of CBtar.
Now, you may mention blissey, but skarm is so much cooler ;) I mean, whio likes blissey? (No offense to those who do BTW.) Also, Skarmbliss killers often focus a lot more on destroying the puffball. With a few adjustments, you can use this to your advantage and show the power of skarmory.
So there you have it, Skarmory, the kewlest and strongest wall eva! lol