The best weapon that I have come across so far, even better than the Drake Sword is the Titanite Catch Pole. Its stats are:

Physical: 120 +17

Magic: 145 +2

Now I know the Drake Sword has physical: 200+ but the Catch Pole has been absolutely dominating all monsters I have come across! Best weapon (that I can wield) that I have found.

I got the Grand Dragonaxe (or something) but I do not have the required Strength (50) to use it. I do have this sickass battle axe and crystal sword, though.

I got a Black Knight sword to drop from the knight in Undead Burg. According to the mini guide it's a rare drop and that guy doesn't respawn so lucky me.... 205 attack and can upgrade it with regular stuff. Still need enough strength to 1 hand it though.
 
@Vitalise: Where did you find that catch pole?

I've been using Quelaag's Furysword (+5) for a while which, with my current stats, deals 162 physical damage + 270 fire damage for a total of 432 damage. I've beaten every boss since Ornstein & Smough with it, with the exception of the Centipede Demon, as he's pretty resistant to fire.

Well I've only just beaten the Moon Butterfly because I'm playing the game in little 5 hour segments. Drake Sword definitely helped out, killed the thing on my first try (Moon Butterfly) . It's the best early game weapon, all you need is a bow and like 100 or so standard arrows. Just look it up and you'll see how easy it is to get it.

@SuperfluousMoniker: It is in the Undead Parish where it connects with the Blackmoon Forest. I presume you haven't been to Blackmoon Forest, because you have to defeat this really touch enemy to get to it. This enemy, Titanite Demon, is blocking your way (you can run around him) and he drops the Catch Pole. Now I don't know if it drops every time, but I was lucky this time haha.

To be more specific, in the Undead Parish where you have defeated the Armoured Boar, and unless you bypassed a big armoured guy with a big shield, you'll have to defeat him too. The big shield guy is in the church and once defeated turn right (from coming in the front entrance) which brings you outside where 3 enemies are. You will see a bridge and that is what you'll walk across to get to the next bonfire. Walk along the bridge and go down the stairs to the bonfire. Below that is Blacksmith Andrei and you'll see a door leading to the Titanite Demon.

Good luck fighting it, and I hope I explained enough so you can find it.

@Vitalise: Is this the lightning guy with the giant staff that kinda looks like he's taking a knee? He dropped nothing for me.

Granted, I had a cover-based arrow shootout with him, so maybe if I had the sack to hit him with something pointy, I would have been rewarded for my bravery.

On topic, the best weapon I've found so far is Astora's Straight Sword on my Faith-based guy, and the Baldur Side Sword (now +5) on my Dex based Thief.

Neither of my characters have the strength to wield the Drake Sword, nor the Zweihander I grabbed from the graveyard near Firelink. I'm only a few hours in, though. I'm sure I'll get better stuff as I go.

Incidentally, does anyone know where I can get a good bow? I still have the short bow that I grabbed from a jerk in the Undead Asylum. My Thief is pretty dependent on his bow, and I'd hate to waste good materials and souls upgrading the shortbow...

I can't really find anything better than the Black Knight Sword. It's pretty shitty and I really hope I find something new that'll scale well with my high strength =/

I'm only just finished beating the Gaping Dragon.

@Red_R0B0T: Yeah it was that guy. Guess i was just lucky that I got the weapon, cause its so good. I have seen a video where there are other places with that enemy, I'm pretty sure. But you will have to ring both bells first and its the place where you cannot go at the moment due to the huge locked gate near that bonfire above the blacksmith.

@SuperfluousMoniker: Everyone is comparing twinkling titanite to colorless demon souls, which makes me think that they may be limited supply, so be careful how you use them. I know the crow at the asylum gives twinkling titanite for a couple of things (give him one of each type of moss clump).

Edit: Just saw a gamefaqs thread where someone said twinkling titanite is farmable later on (in the hollow)... so take that however you like.

I'm using a +1 dark knight sword right now. I found the dragon greataxe or w/e but 50 strength is way too costly lol.