Top 10 odd D&D weapons

[Dioltach]

If a cat hits you without its claws drawing blood, it will still bruise. Those pawsies can pack quite a punch.

 

[Orius]

D&D players are well aware of the lethality of housecats.

 

[Dannyalcatraz]

A few years ago, I read a news article about a man who had a fatal encounter with a feral housecat.

 

[aramis erak]

While I am far from an expert on medieval weaponry, and I appreciate artistic license, there are some weapons proposed for D&D 3.x that just seem mind-bogglingly impractical. Perhaps somebody can point out the utility of some of these beyond being "kewl."

1) Whip-daggers: Did anybody ever actually create such a weapon? Whips strike me as falling into the category of "agricultural tools used as improvised weapons." What would be the point of tying a dagger to the end of one, rather than just learning to throw knives?

Not daggers, per se, but small weights, or an animal's vertebra, have historically been documented. It's a method for making lashes much more bloody. But it's not used on the long whips.
Japanese weapon-on-a-chain type weapons are known, but actual use of them in battle isn't something I've seen documented. The best known is the kusurigama, documented to have been used off the battlefield, but not on it. A number of Japanese weapons have interesting "this isn't the same thing as the prohibited thing it looks so much like"....

2) Sugliin: Here you have a big wrack of sharpened antlers so unwieldy that you have to spend two feats just to use it as a normal weapon. The tactical problems for this are mind-boggling, especially given the fact that you'll probably draw the eye of every archer in sight.

Scaling error... but people have used antlers as weapons historically and pre-historically. And as tools - mining picks.

3) Mercurial Swords: Explain the attraction of a using a deliberately unbalanced weapon that is likely to spew a highly toxic substance if sundered.

Mercurial swords are rumored to be an 18th C attempt to improve swords. SCAers attempting to create them have found them pretty much worthless at increasing the impact force. There are documented surviving metal bead swords, as well... but that's not much better.

5) Musical Instrument Bayonets: Presented in Song and Silence, and instantly ludicrous to anybody who has actually used a real musical instrument. If you want to destroy your instrument in combat, just whack somebody with it.

Yup. Total ignorance.
There are, however, a few instruments that have been used as defensive and/or last resort weapons...
The military fife is a open-hole closed end transverse flute. Some are metal (often copper, brass, or bronze), some are wood with metal findings on the ends. Most musicians weren't targeted, but when they were, they often would defend initially with instrument, and a fife sized baton is a decent parrying weapon and force concentrator.
The drummer's drumstick, likewise.
There are some stories about steel Fue (foo-ay)... the fue being just a tube with particularly placed holes. A sufficiently strong person could easily use that 2-3 foot long
Any others are unlikely to survive such use.

7) Caber: If I recall correctly, this was offered in Masters of the Wild. It was a log that you throw at people. I never understood why this counted as a weapon rather than as improvised use of scenery.

Scots humor at its best. It's been rumored as long as the Caber Toss has been a thing that some Scotsman tossed a log into an English formation. No evidence that it actually happened.
That said, a sufficiently strong individual could do so and disrupt a formation. It's plausible, but not documentable. And, due to the nature of the wounds it would cause, would not look like battle injury, but a logging one. Hence not provable.

8) Two-Bladed Sword: This weapon led directly to one of the oddest miniatures from WotC, a man in full plate armor wielding one of these. That would probably be the only way to wield one without slicing off your fingers, come to think of it.

The historical multi-bladed european weapon I've seen written about is a parrying dagger in the 18" range - the border of short sword vs dagger- the additional blades are 30° off from the central, and only about 10".
The Madu isn't technically a sword, but it's a buckler with a dagger down the bottom and another out the top; traditional indian versions used horns, not blades. SCA use shows it to be practical, but not a great primary weapon. Sword and Madu put a few blokes on the Principal thrones of Oertha. The Maduvu form lacks the shield, and is essentially a handle with antelope horns opposed directions. I've been tempted to make one for SCA fencing. Both Madu and Maduvu are documented.

9) Spike Shooter: This appeared in Races of Faerun. Any weapon with a spike on the end could be set to launch it as a spring-loaded surprise. Possibly inspired by giant robot anime, I don't understand how you could avoid accidentally shooting it off whenever you swung your battle axe.

The big issue isn't the accidental discharge, but having enough force out of it to go any distance at all...
The historical closest equivalent is a gun-sword. The hilt has barrels that fire along the blade. They were impractical, especially since the era of availability was percussion cap era, and muzzle loading....

10) Icechucker: Ah, here we have a crossbow designed to fire icicles. Oh, and it can fire javelins too, if you actually want to use something balanced and aerodynamic.

You don't need a special one - just cooperating weather and a big enough bow. Not terribly effective, tho'.

Having been hit in the shoulder with a falling icicle in the 20 lb range... hurts.
A couple guys from school took icicles to the head resulting in serious concussions, so plausible, but unlikely, an it's going to be a blunt weapon.

That said, I have seen a kid stab another kid in the hand with an icicle. Both left school... one to the ER, the other to the youth incarceration facility.

Bonus) Vulcanian Thunder Club: This was originally printed in Dragon #304, and it made it into Paizo's Best of Dragon Compendium. While I like the book, I am less enamored with the idea of a greatclub filled with alchemist's fire and shot. It is never explained how you can set it off with the pull of a string, but not by whacking it against your foe (possibly inadvertantly).

Pretty easy - Gunpowder's not terribly easily pressure triggered. (If it were, automatic weapons wouldn't be possible, and Gatling's gun goes back to before the USCW.... pre-1862) But wind that cord around a striker wheel pressed against a flint, and those sparks ARE hot enough to start the deflagration. The real issue is that it should spill, and won't have useful high mass.

There are a few more that come to mind, but 10+1 will do.