I'm sorry, your character idea is too awful.

[Badwe]

I always wanted to play a Necromancer in 3rd edition, owing to having fun with such things in Diablo II and Warcraft 3 (and eventually, world of warcraft), but it never really manifested, there was always some kind of a hiccup. In 4th ed, the game doesn't even pretend it wants you to be an evil character, and that's probably the better way to go over letting a player foolishly think they could be a necromancer or other evil character.

I think evil parties work better than evil characters, and even then "evil" is more like "unaligned" or perhaps "mutually loyal to an ostensibly evil overlord". Much of the raid and loot mentality of old D&D is decidedly self-serving and potentially non-good anyway, especially if it's not orcs or goblins you're chopping to bits.

In retrospect, though, if I was the DM, I would have wanted to try to prevent necromancers too.

 

[Dausuul]

Well, I've informed one of my players that before the end of our current campaign hiatus, he has to re-spec his character as something other than an artificer. I just can't stomach the 4E artificer fluff. (I originally allowed him to play an artificer on condition that he re-fluff every single one of his artificer powers; but he never really got around to it.)

 

[Deset Gled]

I believe that most character concepts can work if the player is willing to put in the effort. If a player is not willing to work the character concept around your campaign, it's a good sign that they never really planned on making a functional character, anyway.

For examply, I have seen builds for a small-sized barbarian that work well - add in skills like UMD (3.5e), multiclass for a couple of levels, and you can make it work. I have also seen someone build a halfing barbarian with 6 strength, 10 con, and nothing but melee combat feats that is pissed when his character dies in the first combat that he rushes into.

As for multiple personalities, there are a couple of ways it could work. If the player wants to go the creepy, mood changing route, a wizard with low wisdom and two completely different focuses of spell choice could work nicely. Alternatively, just allowing the player to have a cohort or familiar that they control may appease their need to command two different personalities in the game. A character that suddenly changes personas and forgets where he is, though, is right out.

 

[ProfessorCirno]

The two characters that stand out to me are:

1) Giant talking intelligent jumping spider. See this: (Warning, it's obviously a picture of a spider! http://i38.tinypic.com/xeh8g9.jpg ). It focused almost entirely on stat-draining poisons (with enough other oomph if the enemy was resistant or immune to poisons to not be worthless) and was the party's outdoorsman. He also talked in a very high pitched voice and constantly commented on things being "cute" or "neat." Have I mentioned I thoroughly enjoyed the Exile and Avernum series?

2) Very dapper necropolitan halfling Dread Necromancer (Who would be illegal in just about every way imaginable in 4e . He was even lawful neutral). Intimidate was replaced by "Be obscenely british." His undead were all given names with Jeeves and Charles. To be fair, this fit in very well with the setting, where things were very undead-y.

 

[abyssaldeath]

I once played a male Dwarf fight who was a closet homosexual. He would always insult the elf in our group, but I would make Freudian slips about how cute his butt was or how long and sexy his hair was. The best part was I didn't make that decision until I started playing him. Everyone got a kick out of it. I got a kick out of it because I got a lot of confused lots for about an hour.

 

[Hella_Tellah]

Alternatively, just allowing the player to have a cohort or familiar that they control may appease their need to command two different personalities in the game. A character that suddenly changes personas and forgets where he is, though, is right out.

It's for an upcoming game of Mage: the Awakening (not the PbP I'm running on this board, if my players there are reading), so I initially suggested he spend merits on a Sleepwalker Retainer--a non-mage character who can witness spells without ruining them. It's more the latter thing, the sudden shift in persona, that he's after. Given the darker, more roleplay-heavy tone of Mage, I think playing a character who is that deeply unstable would be a huge liability for the Cabal as they try to make a name for themselves in the local Consilium.

 

[Aeolius]

A two-headed Elven Vampire Wizard (See having two heads he could cast two spells a round). I just looked at him, to which he replied "Its not stupid". Based on that, I never invited him to my game.

This was the inspiration for the BBEG in my current game:

She is a bard.

 

[Starbuck_II]

- Evil characters, because the people who ask to be evil in my particular groups want to either kill everyone in the group or just want to be able to say they wiled an unholy sword. There is no deeper reason.

Exactly, get Use Magic Device (fake alignment) and now you can be a good guy wielding a Unholy Sword: no need to be evil.

 

[Hella_Tellah]

Very dapper necropolitan halfling Dread Necromancer (Who would be illegal in just about every way imaginable in 4e . He was even lawful neutral). Intimidate was replaced by "Be obscenely british."

I'm going to demand that you, also, come to my Wednesday game. This character would be a perfect fit for my Victorian monster hunters game.

I once played a male Dwarf fight who was a closet homosexual.

My buddies have a running joke that this is what Gimli and Legolas are all about.

"Dwarven women look much like Dwarven men! Sometimes I get confused!"

 

[Fallen Seraph]

I would say I get mostly frustrated when a player uses the same character concept throughout numerous games and settings even if they don't make sense for the character.

For instance, one person adores this whole; mentor training two friends in bushido and the mentor dies and two friends become rivals.

Well, he wanted that for a Promethean game set in the American Mid-West, katana and all. All the Prometheans too were newly created, so made even less sense. I put my foot down on that.