Well, one exception is the Zweihander, I used that thing for most of the game until I got the BK Greataxe. Maxing most mooks kiss the floor with a single downward swing feels great.

And yeah, as other dudes have suggested get a weapon that scales, or at least a better dragon weapon if you're really are into those. Why not havel's shield? it has some great resistances against pretty much everything, since you said you already have the set.

Requirement: Strength at 50, my current strength 43, cost to level up stats as of now around 50,000 souls :P

I think Quelaag's Furysword only requires a few extra dexterity from what you have (I haven't seen its requirements since last March so I may be wrong) and it is a good sword

Got it already but since I am in the DLC levels all the bosses are resistent to Fire, Lightning, and Magic.

It also got nerved like all elemental weapons but I would say it is one of the very few extra weapons (the ones requiring sparkling shards or demon titanite) worth using. The black knight weapons are also rather mediocre besides maybe the halberd. They also need quite a high dex stat.

For strength build either the man serpent greatsword which is pretty fast for a strenght weapon and nearly the only choice if you want to go with a dodgy strength character or one of the demon weapons are good choices.

The claymore now sucks after the upgrade because it is so slow and the zweihander is a bit hard to handle because you have to really use its range and time your attacks. They are both also weapons for quality builds (strength and dexterity) because they scale on both.

I need help again:

In the Abyss Darkstalker Kaathe is supposed to be here, but he his not, how do I get him to appear in The Abyss?

Darn it :(

I have clocked an unholy amount of hours in this game but until last week had never actually tried NG+ because I had so much fun starting new characters with all kinds of restrictions. Last week I finally went NG+ and after reading it was supposed to be very hard I took an unrestricted character. Now I'm half way through NG++ and I have not died since somewhere in NG+.
Is this going to get harder if I keep playing or is the difference between NG++ and, say, NG++++ only very marginal? If there's not much difference I might be better off just starting over, but given that my character has long stopped getting more powerful I kinda have hope the difficulty can catch up with me. Anyone with experience of the many ++++++ able to enlighten me?

Numbers wise the highest jump in difficulty is going from NG to NG+. After that the difficulty boost of each next cycle is easily countered by the character levels.

Ah, that's what I was worried about. I shall make a new and utterly restricted character then to prolong the glory that is Dark Souls. Thanks for the info!