What does "might" mean?

[Addict]

The question should really be what does might do. When it for example stands "+3 might" on a composite longbow what does it then mean? And what weapon is best for a rogue (ranged)? A heavy crossbow or a short bow? And is there any difference between the heavy- and light- crossbow more then the damage stats?

[Legolas]

Normally, a bow with the Mighty +3 property requires that you have a +3 STR modifier or better to be able to draw it, and as a result of the extra tension you do +3 extra damage.

In NWN, it's something like that but not quite. Anyone can draw the bow, and the damage bonus is equal to your STR modifier up to the Mighty value.
So a rogue with STR 15 (modifier +2) firing a Mighty +3 bow does +2 damage. The same character with a Mighty +1 bow only does the maximum +1 damage despite being stronger than that.

The Ranged rogue is, in most cases, probably better off using the shortbow. Bows can be fired more rapidly, which is an advantage. Crossbows do more damage though, which makes them better suited for defeating enemies with high damage resistance. If you can cast Bless, you'll always want to take the crossbow when fighting Raksashas.

The differences between Light and Heavy crossbow are damage, weight, size, and weapon speed. In general, the heavy crossbow is superior unless you go after casters. There, the light crossbow has a better chance of disrupting spells (and the bows are better still, but the sling's the champion).

[ZFR]

Might means that strength bonus is added to damage.

[shadowolf03]

The sling is the champion of spell disrupting? Is that what you meant? Or are you saying that the sling is the champion ranged weapon?

[Legolas]

The sling is good for spell disruption.

The other things to keep in mind are that
- The sling is a blunt weapon where the others are piercing (helps damage reduction)
- The crossbow has a slow reload speed (can be fixed with the Rapid Reload feat)
- The crossbow can't be used in Rapid Shot mode, unlike the others (needs a feat or two)
- The crossbow has the greatest threat range (helps damage reduction)
- The bow does most damage on a critical (helps damage reduction)
- Crossbow does more average damage than the bow which does more damage than the sling
- Crossbow bolts can be enchanted with the Slay Raksasha property
- Thrown weapons are a different but equally interesting story, and could also be considered

I prefer the longbow of all ranged weapons, as they compensate for the -2 damage opposed to the heavy crossbow with more attacks. Especially in the case of a rogue this is more useful, because on, say, a +6d6 sneak attack you really don't really notice the loss of a few points (a reason you'd consider the sling, also).
Also, a 20 x3 threat range is preferable to a 19-20 x2 unless overwhelming or devestating criticals are involved. Keen too gives the advantage to the then 17-20 x2.

On the whole, it may even be a good idea to carry some of each type of weapon around. You never know when they might be useful. The crossbow does do significantly more damage facing hard to hit creatures immune to criticals and sneak attacks. With the easy to hit ones, the longbow would be better again for its increased firing speed.