Best weapon for a magic user?

Well I'm not a complete magic user but I still use magic alot and I prefere the Blue Blood Sword. It's strong and can be enchanted to make it nearly unstopible. On my first run through when it was enchanted with Light Sword I could kill a Red Eyes Knight in one hit if I tried. You can only get the Blue Blood Sword if you use the Pureblood demon's soul though, so if you already used it you'll have to wait. The Dragon Long Sword is another favorite of mine. It has physical damage and fire damage. Those are two of my favorite one hand weapon and I do use the dark silver shield with it.

I use Rune Sword and Rune Shield ( Ostrava's Weapon ) the power of the rune sword increase if you have high magic level

Well, I know it's a few days past the original post, but I'd like to post my answer here for others who may have the same question.

In my opinion, as a magic user you should only be using your catalyst as a primary weapon with one exception; the Lava Bow. The Lava Bow should be used to snipe and clear out enemies from afar, which is something you cannot do as a magic user. Additionally the Lava Bow will "stun" most enemies as they burn, which is especially handy when trying to keep them in place, such as the first 4-2 Reaper, who, when you snipe him, starts moving down the path.

The other weapon you will need, which you will use as a secondary, is a +5 Kris Blade. As a magic user, there is no reason you should not use this weapon as it greatly increases your spell damage. It does not however, increase magic damage inflicted by weapons that do magic damage (example Crescent Falcon +x). The other reason you should use this as your secondary and not your primary is because as a secondary you can use it to partially block (arrows and projectiles NOT melee).

I'd also like to explain my logic for those who do not agree.
1st: You are a magic user.
IMO this means your primary objective is damage output not taking hits or fighting in melee.

2nd: You are squishy.
If you've been raising your MAGIC and INT stats as a magic user you shouldn't have very much in anything else. This means 1-2 hits and you are dead.

3rd: Because you're a magic user and squishy you need to rely on range and dodging.
Going toe to toe with an enemy in melee is just dumb and goes against the whole principal. Use what you have: Spells and Range.
Besides the 2 spells that are within melee range (Firestorm and Ignite) all other spells use medium range and long range.

To have an easier time as a magic user here is a plan I suggest:
New Game:
1. Start as a Royal (Soul Arrow will 1 shot most normal enemies)
2. Play through world 2 entirely to unlock Blacksmith Ed and the ability to upgrade to Lava Bow
3. Raise STR and DEX only high enough to use the Lava Bow (21 Str/ 16 Dex)
4. Defeat Adjudicator in 4-1
5. Farm first 4-2 Reaper with Pure Black World Tendancy for very fast soul level gain
6. Free Saint Urbain and Meet with Patches (Both in 4-2) (Patches sells Heavy Arrows)
If you have already cleared World 2 like I suggested then you already have Patches in the Nexus
7. Raise INT stat to 40 for 6 spell slots (7 is the maximum with the Ring of Magical Nature)
8. Raise MAGIC stat to 99 as quickly as possible (May not get 99 until New Game +. I didn't)
9. Raise VITALITY stat to 99 as quickly as possible.

Spells to use the most frequently:
1.Soul Arrow/ Upgrades to Soul Ray
2.Firestorm (Essential. Get this on your first play through)
3.Warding (Use this until you get The One Time Revival Miracle)
4.Fire Spray (Incredible spell with 99 MAGIC 1-2 shots most enemies for very little MP usage)
Fire Spray is one of the most underrated spells. I will touch more on this later

Miracles to use:
1. One-time Revival (Does not have an expiration timer & can save you from magic attacks where Warding does not)

Items/Weapons of Importance:
1. Insanity Catalyst: Greatly increases spell damage (Not REALLY needed until New Game+
2. Thief Ring: Duh! Always use this as it lets you get in targeting range before the enemy notices you.
3. Ring of Magical Sharpness: Increases spell damage and stacks with other items.
4. Kris Blade +5: Greatly increases spell damage. A must have, use all colorless demon souls to get this +5 FIRST
5. Lava Bow: Used to farm 4-2 Reaper and out of targeting range monsters. Very handy for it's fire damage "stun".
6. Monks Head Wrap: I hate this helmet. It looks stupid and blocks view, but it increases spell damage.

Tips for Magic Users:
1. Use Old Spices as primary and Fresh Spice as secondary. Keep 99 of Both
2. Don't waste a ring slot on the Cling Ring. 1-2 shots and your dead in most cases anyway. User Ring of Magical Sharpness instead to 1-2 shot your foes instead.
3. Learn to dodge instead of block. It will save your live far more often
4. Use Firestorm on Maneater in 3-2 for sometimes a 1-shot kill (Do this as a Blue phantom to impress the meleers ;p). Also Firestorm is your best friend in PvP. It takes getting used to the timing, but it will 1-shot most players below Soul Level 200, unless they have One time Revival active.
5. Fire Spray is your friend with 99 Magic. Use it on most worlds and especially on Player Black Phantoms who like to jump around. You can cast and move forever and most won't get near you. When they see it it doing 200-500 damage they will run like little girls. hahah.

Anyway, sorry for getting a little off track, but it scares me when Magic Users ask what weapon they should use. ;P

Best weapon for magic user? Insanity Catalyst.
You shouldn't really be meleeing in the first place unless you're going enchanter-mage
the sidearms you can use vary on your build.

traditional caster -> Kris Blade (Up magic attack, down magic defense)
hyper caster -> Morion Blade (same as any hyper build)
enchanter -> the biggest weapon that you can find that can be enchanted.

My thoughts.

Items of note:
- Kris Blade +5 (found in 2-1 near the Armor Spider's lair).
It does decent melee damage, and increases your spell power (at a cost of magic defense). The spell power is the big draw here, as it's key in 1-shotting powerful foes.

- Monk's Head Wrap (won by defeating a player as the 3-3 boss).
Similar to the Kris Blade. Further increases spell power.

- Insanity Catalyst (crafted by Blacksmith Ed using the Yellow Demon's Soul and any catalyst).
Increases spell power at the cost of halved MP. It's pretty good... but half MP is a hard sell since there's so much stuff that raises your power without a drastic downside like that. Some people swear by it... but since I like to throw out a random Firestorm, I personally dont use it. Not to slight it... if you're doing your fighting with Soul Light, Fire Spray etc... then give er'.

- Silver Tiara (found in a 3-1 cell).
Increases MP by 20%. Good all-around PvM head gear.

- Phosphorescent Pole (can be won by defeating Black Phantom Lord Rydell in 3-1 with Pure Black World Tendency).
Brutal melee damage, and a slick 1MP per second regeneration at +5. Good for messing around, when combined with a Crescent +5 weapon and a Fragrant Ring.

- Talisman of Beasts (can be found on Black Phantom Scrivir in 2-2 with PBWT, or by killing Ostrava for NPC Mephistopheles).
The advantage of being able to cast Second Chance and your attack spells on one inventory item is invaluble. In PvP Second Chance far outclasses Warding in terms of usefulness and diversity... especially since a single 2-handed hit with a heavy weapon will kill you regardless of Warding. The spell power is fine enough to dispatch most opponents with a single Firestorm using the Headwrap/Kris+5/Ring of Magical Sharpness combo.

- Epee Rapier (found off the corpse in the lower bowl of the 3-2 area, or obtained by killing NPC Mehpistopheles).
The only fire-damage scaling weapon in the game (scales with Magic attribute). A neat little toy for PvM, but not strong enough to be a serious weapon.

- Geri's Stiletto (gained by freeing Sage Freke from his cell).
Steals 20MP per poke at +5. It's another funky little toy for PvM, but too silly to use in PvP. If you're majorly outclassing your opponent, it's funny to just steal all their MP for giggles.

- Rune Shield (found in 3-2 on a hidden ledge, or by defeating BP Ostrava in 1-4).
If you're going to use a shield for whatever reason, this is a good one. Low stat requirements. You've already got DSS, so stick with that as I liken it to being the best shield in the game with ony PFS +10 competing directly with it.

- Rings:
Thief's Ring, Ring of Magical Sharpness, Fragrant Ring, Graverobber's Ring, Cling Ring (if supplementing Vitality).

- Don't bother with bows. You dont need to grind out levels... and if you do, do it in NG+ with Yuria's Soulsucker spell (the 3-3 BP Squids give insane souls in PBWT with Soulsucker). To handle a bow is largely a waste of good stat points for a bit of early convience. I suppose this is an advanced attribute allotment for a tuned PvP build... leave it at your discretion to use a bow or not.

To answer your question, pound-for-pound the Asian swords get incredible mileage on damage, speed, and stamina use at the cost of range. Shotel does the least damage, but slips 50% of all block damage which suprises the hell out of people (also small Asian swords stun chain-combo, allowing you to just drink your stamina bar in an attack).
Uchigatana is the big dog of the Asian weapons, and it shows. Great range, good stamina usage when compared to the larger weapons... it also hits very hard. Excellent weapon for NG+.
Daggers are quick, and exceedingly damaging too considering that they're daggers. Like Asian swords, they also stun chain-combo.
If you're turtling a lot behind your new shield... estoc, and winged spear are both excellent canidates for Crescent upgrades allowing you to hide and counter-poke.

Best weapon for magic users is
-> Moon Uchigatana +5

Damage: 143/160/0 (Physical/Magic/Fire)
Bonus Damage from Status: E/E/C/- (Str/Dex/Magic/Faith)
Bleed 180
Req: 18 str, 13 dex

My Royal have:
Str 30
Dex 40
Magic 55

With Moon uchigatana+5 i have 418 dmg (one-handed), and it is a fast attack weapon

In my opinion talisman of beasts is better than insanity catalyst but is harder to get, insanity catalyst HALVES your mp which is hinderence untill high int level and talisman of beasts has more mage power+ it can cast miricles. Note that this is just my opinion and being a mage barbarian myself i use the talisman of beasts. Yes i know maging with a barbarian seems stupid but it actually works pretty well.