Okay...this line of questions had Luke Cage in mind, so information
regarding him specifically is preferable, but anything relating to other,
similarly unbreakable types is welcome too.
Failing any "factual" (ie from a comic) evidence, I'll settle for opinions.

Luke Cage...unbreakable skin...would he experience trouble with rashes, or acne?
How about his teeth? Would they be vulnerable to decay in the usual fashion?
And is his hair/beard/etc tougher than normal or normally cuttable?

Okay, I read this, really thought about not answering took a deep breath sigh-ed and now I'm typing.

I would imagine that he could suffer skin issues like any other person since the bio-chemistry is in fact his own.

As for hair of any type I would think the hair would be normal. Since he cuts it and it has never been addressed as being "tougher"

One could possibly compare the legendary Samson who was incredibly strong but whose power was derived (or at least perceived to be deprived) from his hair.

As strong as Samson was... it took no additional effort to cut his hair then it would take anyone else's.

Luke Cage is exceptionally strong and has "unbreakable" skin. I'm not sure what limits that's been tested under but I don't think Logan has ever attempted to test his admantium against it. I'd be curious.

I remember a comic years ago where Hulk hit Cage and he flew up and through several NYC buildings he seemed to come back from that so he's certainly tough but I don't really know more then that. I kind of think he's probably on par or a bit above par with the Wrecking Crew who are bestowed their powers by Asgardian magic.

He wore an afro and a yellow, open cut shirt. He's got to be CRAZY TOUGH to sport that stuff openly in the 70s. :D

He was knocked off the balcony of a top floor penthouse in New Avengers, crashed on the ground below, got up, took the elevator back up, and rejoined the fight no problem at all. Seems tough.

But then he was hit by an energy blast in Secret War and suffered internal injuries, and the doctors couldn't break his skin to perform surgery. Not so tough.

But as for the original line of questioning, although his skin is unbreakable, it would still follow the rules of normal skin otherwise. If he can still grow hair, then he can still shed dead skin and cut his hair normally. If his skin was completely unbreakable, his hair wouldn't be able to grow through it. This obviously isn't the case.

As for weaknesses, the Ultimate Alliance video game says an adamantium weapon can penetrate his skin, but I don't think there's ever been an example of this.

See but Orin here's my thinking. Hair doesn't really rip through your skin we are born with pores. Hair grows through our pores. We even have pores on parts of our skin that don't generally produce hair.

Like wise a blunt object or sharp object would need to hit the skin where as an energy weapon might effect the person more so because energy like radiation can be absorbed through the pores so I think there's some logic to the examples you sight.

You'd imagine that his bones and organs are also tougher as well since they don't break when he hits a wall or fall from a penthouse balcony otherwise it's like encasing yourself in a steel case and throwing yourself off a cliff. Sure you didn't directly hit the ground but the vessel you traveled in did and your organs and bones would probably burst upon impact. Overall I think unbreakable skin is just a more unique way of him saying he has Invulnerbility.

On that note, it always bothered me on shows like Buffy, or others like that where people are throw through brinck walls. Because I don't care how hard you are thrown, bricks win. A nerfball thrown at 100mph won't go through a tree, if you get what I'm saying.

If he has unbreakable skin, couldn't his insides still be turned to jelly?

Well that's just it I mean many characters have origins that make their powers somewhat more logical.

I remember years ago reading a hypothesis on how Superman might exist based upon the differences between Earth and Krypton. A.) Higher Gravity on Krypton would give him near weightlessness on Earth and he could jump extreme difference (Flight) but he probably could not stop or change direction in mid-air. Low Gravity might also give him some sense of super speed. B.) Perhaps the atmosphere of Krypton is far more abrasive and therefore a kryptonian's skin might be much more resilent or dense and this might explain why bullets could bounce off. It went on like this and discounted things like how a different colored sun would probably have no distinguishable effect.

So I think there are ways to accomplish hitting a wall and going through without becoming a pancake.

I mean a few factors to consider and I should tell you I've gone through a wall or two in my day granted neither time was the wall solid concrete or steel.

The bigger you are in weight and mass the better your chances since you cover more area your impact would be dispersed over a wider area. They recommend when falling from a height to try to spread out your body so that you don't impact all on one central limb or point. Personally I advise don't land on your head.

Obviously the bigger you are the better your chance of breaking through a wall. I've gone through a wooden wall where the wall literally went down... the whole wall so that I landed in a room with only 3 walls with the 4th wall under me, more or less. I also went through a cinder block wall where the bricks just came free because the masonry just broke away. So I ended up knocking loose enough bricks. to pass through and a few surrounding ones were just out of place.

I'm 5'9" and 235Lbs. I'm a former boxer and I bartend which means I occasionally have to bounce a few people and most times they go easy but sometimes it doesn't go as planned. In 15 years of tending bar I've had a handful of brawls and as a kid I grew up in a tough neighborhood. So yes you can surely go through a wall but I would imagine not every wall, not every character's resistance to damage is the same and I do wish we could see that dealt with from time to time just from a developmental standpoint in comics.

As an example Wolverine and regeneration. Yes he can heal from most anything but I'd imagine it all still hurts like a dickens.

The whole skin and muscle vs. internal organs and bones issue comes up again when you see feats of super strength. I mean Okay you can lift 20 tons like Spider-man but your skeleton must be equally strong not to collapse under the stress of such a load. I mean leverage is one thing but I don't see most characters in a comic book stopping to consider the best way to throw this armored truck at that charging behemoth coming at them.

That was always a big drawback with the Bionic man set up.

Has Luke Cage ever had a beard?

I don't think he has ever had a full beard that I recall but he sports a goatee.

A good thing it is you didn't break the 4th wall. Seems like even She-Hulk and Deadpool has stopped doing that.

I was hoping for a few more opinions here.

Also, how about junk shots and eye gouges?
How would Cage's power set cope with them?
How well could Cage pull off that "Shot in the eye" trick from Superman Returns?

If you are interested in this type of thing, the whole how would those super powers really work kind of discussion, you may want to google "man of steel, woman of kleenex". An interesting analysis by SF author Larry Niven on whether or not Superman and Lois could actually produce children.

Warning:While not quite R rated, but it does deal with the biological aspects of reproduction in some detail.

Yes, I've seen that, and was amused.
My interest here though, revolves around the less obvious vulnerabilities
of someone with Luke Cage's power set.