Whether the weapon has a bad design, has a useless power, or even a lack of story relevance, I am curious to know which weapon you hate the most! Here's an example
They aren't even Bonkle pieces 
You can also add which one is your favourite, if you have one.
I'm gonna jump on the Squid Launcher bandwagon. The weapon doesn't look half-bad, but why on earth would you use a living thing as ammunition? What's to stop the vampiric squid from jumping out of the launcher and sucking out your life-force?
I disliked the Cordak launchers. They were tricky to use, clunky and frankly didn't look very good IMO.
Lets add to the launcher hate, the Midak sky blasters suck as well, they're a massive silver tube that doesn't look all to well with most figures and can actually be kinda heavy. and theres no build potential, just slap the launcher on and done.
Pretty much the only launchers that are good are the Thornaxx launcher and the stud shooters, and the thornaxx is only kinda good, cause it can be built into other builds very easily, but still only has one shot.
Either the rapid fire stud shooter, or Gali 2015's entire weapon.
The Skull villains' hook blades. Not the axes, the swords. They just seem so useless, both in canon and as a piece. Maybe there's a hidden potential I haven't discovered yet.
My favorite would be Gali Mata's hooks or Onewa Metru's tool-things. I like that they're used for climbing.
The worst Bionicle "weapon" is Quake Beast's arm. The build is okay, but just the function is trash. Also every gun-like weapon in Bionicle. Except the Skyblaster and Zamor Sphere Launchers.
The best weapon in my opinion is Onua 2016's hammer, because the dual function of the drill and stud shooter worked well imo. Another one of my favorites was the axe that Axonn used.
I'll agree the Midaks are bulky but the Squid Launcher is the worst based on it's firing mechanism, the rubbery plastic of both the gun and the ammo.
Definitely.
I dont like this ones they look odd to me
Lest we forget the nyra ghost blasters. Even cordak blasters were more reliable than those pathetic things.
My Nynrah ghost blaster actually works better than my Cordak blasters...
Regarding launchers, I wasn't too big on the look those clips gave the Inika's Zamor Launchers. Yeah extra ammo is nice and all, but it just made the launcher look really bulbous and awkward.
The Squid Launchers were cool conceptually, but were ineffective functionally, only working on a case-by-case basis for me.
Much as I enjoyed the Midak Skyblaster, it only really looked good on larger vehicles and Titans. That, or mounted like a rocket launcher in Pohatu's case, or as a two handed weapon with Kopaka. Lewa and Toa Ignika just looked strange lugging this massive blaster around in one hand.
As for melee weapons, I didn't particularly enjoy the designs of the Inika's primary weapons. They just felt unappealing visually and the light up feature felt unnecessary and gimmicky.
I remember feeling large amounts of anger when trying to pose 2015 kopaka with his stupid shield. So I guess I'll go with that.
Squid launchers.
Urrrrrrrrrrgh!
I never liked the fire tools Vakama Hordika had.
Some of the playset weapons were notably bizarre.
What even are those things the Piraka have... Big screwdrivers?
I'm as perplexed as you are; the only thing they remotely resemble are tasers to me
Umm, a certain steef would disagree with this, (Oddworld reference)
I think that live ammo is a cool idea, but the blasters were bad functionally
They are actually pieces of ghost hunting equipment...
best: 
worst:
and