Fighter and fighter kits can get 4 pips in weapon proficiency at level 6 or above. Dual to something else can get grand master in a weapon.

Fighters get another 1/2 attack per round at level 7.

So a fighter dual at 7 is more powerful than a single class fighter, and also very powerful at the second class.
However, there is an experience cap in the game, a fighter dual at 7 can only work with druid, thief and mage, otherwise, cannot reach level 8 in the second class, which means game over.

You can reach level 9 druid, or level 8 mage or level 8 thief.

As for the fighter class, the best kit is berserker, and the other kits are not worth it.

Unfortunately, berserker, druid or thief cannot use the best weapon in the game, which is a lot better than any other weapon. So the best class is a fighter dual at 7 to a mage

Actually, Baldur's Gate 1 has no kits, so berserker doesn't qualify here.

Anyway, when you consider the slow walking speed and the availability of nice arrows, a fighter using a bow is probably the most powerful setup you can get.

Not regaining your previous class's abilities isn't game over; it just means your main chracter (only) will be a bit weaker, and when you transfer to Baldur's Gate 2, you will be able to regain your abilities there.

Of note, if you are using a BG2 mod that lets you play BG1, the Archer kit is quite good. In BG2, the best single classes are probably Wild Mage (if you are willing to use exploits) and Sorcerer (if you know what spells to pick).

In bg1 its Bard:
1. Wands... lets see your fighter take out a battle horror in 1 or 2 shots or spam summon monster to keep a boss away.
2. bow and arrows = special ammo, dispel etc
3. Spells = travel invis, open locks, charm, sleep etc then put your armour back on.

Fighter is the simple class for first time players so best for beginers yes.

The answer is always BARD, regardless of game.

The answer is obvious. The only character class that can solo sarevok is the thief with something else. No Mage, fighter or fighter subclass can go toe to toe with big bad black dude is thief. Although thief doesnt go toe to toe. He just backstabs and rinse and reuse.

I am talking about vanilla Bg1 game.

In BgEE or Bgtutu, then yes fighters can solo sarevok by themself. I have done it. In fact, you can solo drizzt too with a warrior class.

I second this. The Fighter/Thief is the most used class in solo playthroughs of BG1, and for good reasons ;)

Of interest, if you are using Tutu/Trilogy and importing an endgame Throne of Bhaal character (warning: doing so will destroy any semblence of difficulty in the game), here are some things to note:

Fighters are ridiculously overpowered thanks to Greater Deathblow. Combine this with a bow that hits an area for mass destruction. I think even the final boss will die to this.

Mages have Death Spell, which should work on most enemies. Also, all the powerful high level arcane spells from BG1.

Then again, if you do this, I'd imagine that even a mage with no spells could handle Baldur's Gate 1 if the mage is level 20+. In other words, only do this if you want a fast and easy playthrough.

Back to vanilla Baldur's Gate 1, note that druids and mages get 5th level spells with the expansion, but clerics do not. Without the expansion, all three of those classes are limited to 4th level spells (with mages and bards being only 1,000 points short).

Of note, muliclass (but not triple-class) clerics can still get 4th level magic with the expansion.

Don't forget that single class fighters get high mastery, which is available to dual class characters as well. You could start as a fighter, reach 7th level for high mastery and the extra half attack, change into a druid, get 4th level magic, and still end up with 26,000 XP to spare. Alternatively, you could change at 6th level, forego the extra attack (but keep high mastery), and cap your druid level by exact count. In other words, you get decent fighting *and* 5th level spells. (Note that this strategy ignores BG2.)

The Fighter/Thief is one of the best combos. In Baldurs gate 1 and 2EE, the assassin or blackguard in can kill irenicus or sarevok SOLO. Poison weapon if it hits in unison can destroy irenicus in hell, Sarevok in bg1, and just about any other enemy. I used a 3 man party with my cleric, dorn and rasaad. Rasaad got targeted by Irenicus while dorn hit him 5 times with poison, messing up his spellcasting and killing him outright.

Dont know how well that will hold up in ToBhaal.

In Throne of Bhaal, the most powerful class is:
Wild Mage, if you are willing to use major exploits (and are not playing the Enhanced Edition)
Sorcerer, if you know which spells are useful
Mage, in other cases (multi-classes as well, but they take much longer to get 8th and 9th level spells)

Interestingly enough, an arcane caster with Project Image/Simulacrum and a Rod of Resurrection can replace a cleric. Also, with enough Wisdom, Limited Wish can reliably heal your party partially (and even cure some conditions) while Wish can be used for emergency healing (but is unreliable). Also, don't forget that (Dark) Planetars can cast Heal and Raise Dead.

Many non-thief classes can solo Sarevok. I have also soloed Drizzt with non-thieves.

Fighter (7) / Specialist (8) dual-classes are the most powerful in Baldur's Gate; I recently wrote a lil' about them in my tanking and melee section:
http://lilura1.blogspot.com.au/2015/08/baldurs-gate-blathering-part-iii.html

You are late to the party my friend. In fact, it ended three years ago.

I haven't played BG1:EE, Tutu or BGT, but given my experience with Coran in BG1 vanilla, I'd guess that "quite good" is an understatement. Coran is the best NPC archer in the game (it's possible to make a protagonist who's marginally better) and was by far the most devastating character in my party. A character with the Archer kit can end up statistically significantly better at archery than Coran.

all this talk of dual. somehow it never appealed to me. how forward looking is the permanent termination of growth of a given class? that termination would trump any advantage, since you're basically arguing against your character's growth (or at least the half of him u dual'd from). The only exception I'll state is back in Dark Sun Shattered Lands, where a thief was useful maybe five times, i started a thief, then dual'd immediately to fighter, just to have the thief's skills.

But in an epic never-ending line like BG u'd dual? Unless a class is particularly hated in BG, which probably none is, I totally see no sense in this argument. You're talking about an infinite-growth-of-every-class paradigm correct? (NWN-type) So, the question then is which class (the one u dual from & therefore permanently stunt growth in) are u insulting and what then retains the value of play?

Thanks.

(PS: these arguments against dual don't apply to Multi. Even Multi, in cases beyond FC FM or FT usually waters down a character far too much, and even then you have to see if your end-game, or the end-of-some-future-predicted-game, won't cap u below the power u seek)

Remember that, in the BG games, the cap is based off total XP, not character levels; hence a multi-class character will cap out at a lower level than a single class character would (or an early dual class in the second class).

In the long run, I think it's best to compare dual class characters to single class characters from the target class. If you look carefully at the XP table, you can get a decent number of levels in the first class while losing maybe 1 level of the second (and in Throne of Bhaal, levels don't mean as much past a certain point). In the meantime, you get some of the benefits of the first class, which can be quite helpful. For example, if you do Fighter->Mage at level 2, you end up with a Mage who has a lot more HP (9 with average Con and rolls, more if you have more than 16 Con and get a good roll when reaching Fighter 2) and can wield weapons and wear armor (elven chain being the most interesting option here). Similarly, you could get thieves who can use fighter weapons (but not backstab with them) and wear heavy armor, or a druid who can wear plate mail (IIRC, could be wrong on this last bit).

At least in classic, there's also the exploit of going Ranger->Cleric, which will give you a Cleric with access to all of the Druid only spells (excluding some HLAs), getting access to 7th level Druid spells before a single class Druid. (On the other hand, I note that a multiclass Fighter/Druid gets access to Heal before a single class Cleric.)

The Dark Sun games, incidentally, give dual classing two useful properties it does not have in the Baldur's Gate series:
1. You can dual class twice, getting levels in 3 classes; you can also dual class gladiator, but can't multiclass it.
2. Preservers and Psionicists get to choose spells/powers at every level up, but don't get to choose their starting spells/powers (they're fixed). So, if you want more access to spells/powers that you don't get at character creation, you need to dual class, which will allow you to choose spells/powers at level 2 (instead of getting what the game would just give you).
(There's also the minor exploit of going Ranger/Cleric to give a Cleric two elemental spheres; while it's technically an exploit, I consider it fair given how limited a Cleric's spell selection is in the Dark Sun games.)