Every Once in a while you come up with an character idea that Sounds Cool, but dont really work in game.

My most ludicrous character concept has to be my mage, specializing in touch spell.
He was 1 level wizard, and didnt last more than half a battle.

(I'm real popular with my group, I come up with some concepts thgat never should have seen the light of day, and they usually die fairly quickly. When i create a new character, the rest of the group smiles and say "Yey, a new batch of healing potions (or other magical items) for us).

I would have to say that my homosexual half-orc druid -- Gronk "Daisy" Bloodeye would fall into that category...

Started out as funny, but then got really old, really fast.

I don't know what it is, but every time I roll up a...bard, it's like I am somehow placing a big sign on my forehead that says "PLEASE KILL MY PC IMMEDIATELY, DM."

This has happened on 3 different occasions in 3 different games. And, it doesn't matter if I try to sweet talk with the bard, fight with the bard, or run away. He always dies. Always. (Or, the DM decides to inflict him with some sort of terrible affliction so he's a big POS even outside of battle.)

Bards and me, I suppose, just don't get along.

As far as lame? This was back before you could tweak classes, but I had a cleric that wanted to do 2-weapon fighting. he got killed...rather quickly. (And, oddly, there is a prestige class based on this now in the Complete Divine. Some lame ideas just never die!)

The old 3rd level Diplomancer. So lame. It works mechanically, but when you win battles by making friends...it annihilates D&D's party system.

I played an anorexic ADHD monk once in a tabletop game. She was so hyper she couldn't talk coherently half the time, and was absolutely obsessed with portion control. Every time her companions - one of whom was a dwarf - ate or drank anything, she was always concerned about their health, the size of their meal...everything. She was hilarious, and annoying, but absolutely exhausting to play.

That game quickly degenerated to a point where the other players winced when she started to speak.

Hilarious, but short-lived.

My worst character concept was a Human Paragon 1/Ninja 9/Dread Pirate 10

The slightly demented rogue, who happens to attempt to steal anything, but has no ranks in neither hide, move silently or sleight of hand. And a negative dex mod.

Heh, I had an elven fighter/mage/arcane archer (very typical), who became obsessed with the rogue in the group, and started training (cross-class) exclusively in OL, DD, and PP...really pissed off the rogue of the group, and yet he survived long enough to find a deck of many things...where he drew, in order, destroy all magical items, fight with death...yeah.

I made a dwarven monk character who worshipped a god (of my design) called Pax. Basically, the concept was that Pax was the god of worldly possessions. His worshippers were not allowed possessions but they were the caretakers of Pax's possessions. In short, my character's equipment belonged to his god but he was free to use it.

Noone quite understood the concept

That concept makes perfect sense to me.