Just about all of them can be used to make unique equipment. Even if you know you don't care about the weapon I probably still wouldn't use them. Souls are endless, but boss souls aren't. You can generally grind out whatever souls you would get from a boss soul pretty quickly.

If you aren't going to play NG+ then I suppose it doesn't matter.

Figure out which you want to use for making equipment and consume the rest, I have yet to consume one even after being a few NG+'s in as they don't drop more than once a playthrough.

If you have an idea of what kind of weapons/armor you are aiming for then check to see if any of that equipment requires a boss soul to craft. If not, I don't see any reason not to consume them.

id say keep em. Look up what weapons you can make with them. I always get iffy when i think of popping one. Theres always something to farm

Hell no! You're crazy for even considering it! You can usually get the souls they give fairly quickly, and since they only drop once per playthrough and are needed for unique weapons...

Honestly, I'd say look at the ones you would consume on the wiki and if you aren't interested than get em.

Honestly, the only good soul weapons I've had are the moonlight butterfly spear (for my sorc) and the greatshield of artorias.

There are only one or two boss weapons worth anything, at least for my balanced build and my unwillingness to use Chaos.

I crafted all of them because I'm stupid. If you're not interested in trophies, pop those souls.

And have a look at the Wiki, unless you're averse to any insider knowledge. It'll give you a good idea of which boss weapons to craft to fit your style, if any.

EDIT: They aren't worth that many souls, comparatively, but, hey, they do more good as levels than as unused weapons filling your inventory.

You can use the souls to craft really strong (and good looking) weapons

As others have said, check if the souls are used for something you want before doing anything. Don't consume them either. I think most of them are worth more to be fed to Frampt.

Thank you for all of the advice. I've been playing again for a few days and I'm really starting to enjoy Dark Souls more than ever. Just rang the second bell and got to Anor something. I think it's time to upgrade my Drake sword so I may do some boss soul research like you've recommended.

The most helpful thing anyone can tell you at this point is to drop the Drake Sword as fast as you can. You do not want to use the Drake Sword past Sen's Fortress. You should have stopped using it back then. Check out the other weapons you currently have and see what move set you prefer. After that upgrade the weapon as far as you can. If you haven't been increasing your strength or dex stat check your preferred weapon and see what it scales with. There will be a letter grade next to each stat on the weapon stat screen.

Most of the boss weapons are not that great. Some are worth using for making a cool weapon/shield, but I would say, by and large, using them for souls is a better use for them. Soul of Sif can be useful for the shield, and some people like the furysword from Quelaag. Otherwise, there are much better items out their for the most part. Some of the DLC boss weapons are pretty cool though.

Okay. So, after some reading, I ditched the Drake sword in favor of Zweihander +10. Hopefully this was a good choice.

Zweihander is a powerful weapon. It should serve you well, but it is slow. I recommend getting another weapon as a back up, like a Man Serpent Greatsword, just in case you need a little extra speed.

If it's souls your after and are far enough a long in the game. Farming the painted world is by far the best I have found. Can easily get over 100k for 15 mins of work.

I just got the Lordvessel, thanks to 2 awesome people who helped me out during that crazy fight. My PSN name is DaNizKing (I really hope I can change this with the PS4). If by some chance you are a Giant Bomb user, thank you!

Honestly, most of the boss soul items aren't all that great. Some of them are, but still, depending on your build only one or two will be useful to you and the rest are just gonna sit in your inventory unused.

Like the moon butterfly soul makes a pretty good magic based spear for spellcasters, but if you're not a wizard its pointless. Quellaags soul makes a couple good dex weapons (depending what you use it on) but for non-dex heavy builds, again not so great.

Plus most of them look a bit over the top and "WoWish" that i hate using them even if its good for me. So yeah, eat em up! Boss souls that made armor would be much cooler imo.

I just finished the last boss. He was rather easy, I just tossed on crazy armor, used Iron skin (I think that's what it's called), and had at it. Again, thank you all for the help, once I upgraded my weapon, things got a lot more bearable.

Why does everyone recommend to drop the Drake Sword?

Because it's awful

You can, the weapons are unique in some way but not usually very useful if you just want to play the game once. There are better weapons.

That being said they don't really give you much and you would get more just playing.

Also, you should upgrade weapons more. If you're still using the drake sword at Anor Londo you're gimping yourself unnecessarily. Upgrading the drake sword is costly and ultimately not worth it when you can upgrade a regular long sword (for example) and do more damage for far less.

Also because Anor Londo was mentioned- this:

Pretty sure it's because Dragon Weapons have awful scaling or maybe they don't even scale at all (forget which). Also pretty sure they can only be upgraded to +5. So while the early damage is great, come mid / late game the drake sword will of been passed over by most other weapons due to them scaling much better with your stats or through them being upgraded to +10 / +15 negating the higher base damage it starts with.

You can just grind for souls. Might as well hang onto them.

I consume the Moonlight Butterfly's boss soul every play-through because I don't have any need for it's unique equipment.

So it really just depends on your wanted build.

Yes, but make sure you put a little sriracha on them first makes them taste better.

The soul amounts aren't really worth it, but if you are 100% sure you aren't going to want to make any of their equipment you might as well. Its not doing you any good sitting in your inventory all game if you never use it.