The OP asked for underappreciated perks, not overpowered perks

Hack and Slash, the "bleed damage" perk for war axes, is one I've seen get crapped on in the forum, but is one I found incredibly effective. Especially after the 2nd and 3rd perk point. I had plenty of encounters where I'm fighting a group of enemies with my dual-wielding Orc warrior where he'd land a couple of blows on one enemy then move on to the next threat. While fighting the new threat, the initial one dies from his bleeding wounds without having to go back to him. Certainly helps to dispatch Draugr Deathlords and dragons much quicker, as well.

i was wondering if you were playing on master?

since, i'm on console i have no way of knowing EXACTLY how much xtra damage is being done on that difficulty setting.

and, so, i can't make an informed and precise decision either way.

speech perks, love them on my thief

Woo! Came just for this The Disintegrate perk can be absolutely invaluable. See that group of level 40+ mages that always gives everyone a hard time, even on Adept? Well, they're surrounded by undead, and if you kill one, his buddy will simply raise him right back. With groups of powerful mages, you essentially have to fight them twice. But with the Disintegrate perk, you leave no chance for that. On top of that, it works when enemies are at low health. That means that you can potentially get a one-hit-kill on someone who would otherwise take a few more shots. If you brought down an ancient dragon's health to maybe ten or twenty percent (and, say, there's a freakin' dragon priest nearby), you can switch to a simple spell like Lightningbolt or Sparks to get the job done. I think it's also a bit of under appreciation when people take Block perks to compliment One Handed but ignore the dual wielding branch. For just three perks, you can significantly change combat on the fly and become offensive or defensive whenever you need to be. The specific weapon perks are also under appreciated, as far as I've seen. Of them, the axe perks are the best--almost everything bleeds, and bleeding damage stacks. That means it's already good enough with a battleaxe or to give your warrior defensive DoT if they're using a shield, but two axes can make quick work of anything, even ancient dragons. The right side of the Enchanting tree isn't popular, either. Just two perks and you can now use enchanted weapons with a lot more lenience. Definitely worth the investment, IMO. Obviously, very few people like the Cushioned perk under Heavy Armor. So few, in fact, that most people just use the Steed stone to save them the trouble of getting that perk just to have Conditioning (and I don't blame them). In Smithing, Advanced Armors is under appreciated. People don't like that you don't get weapons or shields with it and that it comes with a heavy armor set. What people don't consider is that Scale armor is cheap to make, valuable to sell, and a whole lot easier to acquire (material-wise) than the components for Elven armor. Also, no one other than myself (that I know of) is fond of creating a heavy armor warrior who uses the light side of the Smithing tree. You get great steel plate armor and lightweight weapons--while they may not be as damaging, that means more weapon sets (for weapon masters/collectors/enchanters) for different encounters and faster-drawing bows. That's all I'm going to go over for now (don't even get me started on Lockpicking), but a lot of the game's most interesting (and useful) perks go unappreciated.

Hack and Slash, the "bleed damage" perk for war axes, ... Certainly helps to dispatch Draugr Deathlords and dragons much quicker, as well.

Persuasion is a good perk to get if you're going for the fence perk. You will level up Speech with a small bounty very quickly - much more quickly than selling loot.

It's sad kind of that a few neat perks are locked up in the Lockpick, Speech and Pickpocket Trees. There are some nice perks in there, but a number of Perk Points have to be burned through to get to the good ones.

I've always wondered how effective the disintegrate perk was in destruction. Anyone know?

The Dinsintegrate perk for shock damage really svcks, for two reasons. 1) The ashes tend to vanish through the ground, so you can't even loot what you just killed, and 2) ashes are bugged and never seem to disappear.

In my last game, there were ashes lying all over Skyrim because of me, and they never disappeared. As I recall, this bug was also in Fallout 3. When someone became a goo pile, that goo pile remained for the rest of the game. You can even click on the goo pile/ashes to talk to the newly respawned enemy, who may be standing behind a tree somewhere. You can hear them say, "Huh?"

Many people say vampires are weak.
A vampire illusionist with the necromage perk however is probably the most powerful class to play.

So I would say necromage, because still many people dont know all the wonderful things it does to your vampire.

Okay somebody care to explain to me what is so good about this perk? Spells work better on undead.. so? I don't see what kind of spells you'd put on yourself except Muffle/Invis. so where's the "BIG" advantage here?

I don't get it..

necro advantages work on YOUR vampire pc.

ROFL! Yeah, "wax key" in the lockpicking tree, it's my vote for the most useless and pointless perk in the game. What were they thinking? When could it ever be useful? If you picked the lock, you'll never need to open it again...why would it matter if you had a copy of the key after you pick the lock? I don't think anyone has ever actually taken this perk.

No, I know this.. someone didn't read. I was asking what the big advantage to that exactly was?

But after reading SQ's post it's making alot more sense to me. That can be abused hardcoe.. and this perk's in Restoration? What rank? (Level)

It's sad kind of that a few neat perks are locked up in the Lockpick, Speech and Pickpocket Trees. There are some nice perks in there, but a number of Perk Points have to be burned through to get to the good ones.