Are there any notable things in the game, when i use a certain race or class. (Like a special dialog if there is a gnome in your party or a weapon only for paladins). I don't want to miss a thing.
I've heard it is necessary to have a dwarf in your party to fulfill some quests - is this true?

What are the best weaponons in the game.

P.S.: Sorry 4 my bad English - but I'm from Germany.

You don't need a Dwarf for any of the quests (at least not the ones that I've done yet) but their high constitution makes them good reliable fighters so I'd advise it. Also one particular NPC "Bonedancer", a group of Fire Giants and a particular Cleric all react differently to Paladins to all the others. For instance, Bonedancer the Nocromancer will happily agure about religion with a Paladin and hold you up, however if you try to persuade him to attack you (only Paladin's can do this twice!) then you'll get bonus XP for being nice (two bonuses if you're a realy nice Paladin), If you act arrogantly when the fire giants ask what you're doing (something like "stand aside, I have business with you're superior") then they just shrug, stand aside and let you infiltrate their area, other characters have to be more diplomatic. There is an evil monster using illusions to pretend to be a good cleric, If he speaks to you're paladin first then there'll be a conversation option to warn him that you sense his evil and he drops his illusiory appearance. Other characters are kept in the dark for ages on this one.

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Balgin, the Dwarf

Bards have special dialogue all throught the game.. easthaven and Dorn's deep are most notable
SPOILERS??


Halflings have a dialogue in lower dorns

Dwarves? i've never played with one, i'd imagine they hate them at the Severed Hand? (there is a special dwarf axe somewhere)

Paladins are the cronic goodie two-shoes.. "hey Paladin, let's just get past this chump and snoop around a bit", "SILENCE! your lies sicken me!" <thwack>

Evil Priests get a dialogue or two (kuldahur pass)

Gnomes get special treatment? where, in dorns? this i gotta see

Perhaps a tiny spoiler?
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You will need a dwarf for an optional quest in the Gloomfrost... but thats all I'm saying.

I created a party using all six races. It was a lot of fun and I'm going to do it again in IWD2.

too many races in iwd2 to have all of them.. hehe

be carefull in creating your party. a fighter can be an asset if the strength is 18/75 (reroll). dont use all the slot for members. try to use only four to gain more experience.

There's a magic item later in the game, (gloves of Elven might) that I think is the only item that takes a thieves strength past 18. But to use this you need to be a multi-class fighter. My advise is to have an all single class party, except for a fighter/thief. Theives don't get anything except more hit points past 15th level anyway.
I seemed to get the same response from The Bonedancer, and all I had was a fighter with 18 charisma. (paladins can't become grand masters with weapons, and clerics take care of healing.
Spoiler for BARD
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If your a bard, you can persuade the Fleezum (the one responsible for the darwing of Marketh) to give up his career and become an artist, but you need to do it before you speak to his brother Flozum. When you enter Marketh's palace, start checking rooms starting on left.

if you have a dwarf in the party at the severed hand you'll get a fireball dropped on your party

Bards also get the Siren's dialogue right at the beginning of the game - my memory's a little hazy, but it's the one with...
Pot Spoiler
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The broken sword that is repaired once you get back to Easthaven.