[Klutz]

Numerous item spoilers...
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Favorite weapons so far. As requested, not based on raw power, and also limited to ones I've actually used (only played through SOA twice and haven't played TOB yet):

Arbane's Sword (D6+2, +2, Free Action, Haste 12sec/day)
Excellent magic item design... well-balanced without being cheesily overpowerful and incredibly useful to a web-slinging thief-mage. Also available pretty early (first between-town-areas encounter I think). Gets my "weapon I most want to build a character around" award.

Staff Mace (+2, 2D4+2, 1-handed staff)
Fantastic starter weapon, available cheaply from Ribald. The only one-handed staff weapon in the game, and note that its base damage is actually well above the usual for a quarterstaff. Never the best for any class, but a good step along the way for many. Jaheira used this in my first game to good effect until we made it to Trademeet and the Druid Grove.

Composite Long Bow (+1/+1, 2 attacks/rnd, 18 str required)
Yes, just the plain old ones you get off every little group of Goblins you kill in Irenicus's dungeon. I'm probably a bit biased since my first PC was an Archer who grandmastered in long bow at creation time (before I knew about all the good short bows), but the mileage he got out of just this bow was amazing. He actually switched back to it (from Strong Arm) in the Underdark when I decided that my Girdle of Hill Giant Strength would be put to better use on Jahiera. It is also an extremely effective weapon for just general Fighter-types who put two stars in it (like Minsc). Other bows shoot more often and have better + to hit/dmg, but it is nice to get a solid usable weapon this early.

Firetooth (+3, 2D4+3, +1-2 fire damage, throwing dagger)
Gets the coolness nod over the +2 Boomerang dagger for its fire damage, but both returning throwing daggers have a base damage of 2D4, instead of the dagger's usual D4. That's the same as a bastard sword, by the way! Very nice bonus for those people that thought they had wasted those proficiency points in dagger, or as a backup weapon for mages that are tired of collecting sling bullets. Firetooth's one downside is that it isn't available until the Underdark, but you can get the Boomerang dagger pretty quickly in the Bridge District if you don't have any qualms about slaughtering some obnoxious adventurers. (I believe the Limited Wish quest lets you get it in a more lawful manner, but I haven't tried that way yet.) Don't forget you can use it in melee mode also.

Improved Mace of Disruption (+2, D6+3, strikes as +5, immune to level drain, bonus damage and chance to slay vs undead)
I know it is considered one of the cheesier weapons in the game, but I really admire the design of the weapon. The combination of immunity to level drain and that it strikes as a +5 weapon make it an effective option against nearly any undead in the game. (As opposed to Daystar, which can be devastating with its Sunray charge but only strikes as a +2 weapon in combat.) The chance to slay may be overpowered, but it is a long way from being the most abusively powerful ability in the game, and you still need to breach against most of the tougher undead (read: Liches) in the game. Minor style quibble: I just wish it kept the original Mace of Disruption picture instead of reverting to the plain old mace icon.