A 13th level elven Ranger, built to spec per UNEARTHED ARCANA...
...who double-specializes with bows...
...who has a STR of 18/00...
...who strikes within 30' (or as close as 6') of a target...
...who has 3 segments of surprise (each segment equalling one round of combat, and allowing triple rate of fire per the DUNGEON MASTERS GUIDE for missile weapons)...
...who does the maximum damage (16) with every arrow, plus adds the +6 to each shot for strength, plus another +3 for double specialization for a total of 25 points of damage (potentially) per shot...
...who hits with every shot (they have surprise, negating any Dexterity bonus the subject target might get, thanks to specialization they are at a total of +2 for specialization, +3 for double specialization, +1 for bows as an elf, +1 for short range for a total of +7)
...who uses the maximum weapon specialization RoF of 4 shots per round (and we're treating segments as rounds, and per the DUNGEON MASTERS GUIDE receiving three times the normal RoF for a total of twelve shots per segment)...
...will deal out 900 points of damage at maximum.
I think.
Someone check my math here.
Dude, lots of errors (and/or rule-breaking) here:
An elf can't have 18/00 strength (max for an elf is 18/75)
The max ranger level an elf with 18/75 strength can attain is 11th
It isn't possible to double-specialize with a bow (or any missile weapon, for that matter)
Therefore the max. damage per shot is 19 (6 for the arrow, +2 for specialization at point-blank range, doubled, +3 for strength)
Surprise doesn't negate Dex AC bonuses (except in crazy 2E-land)
The +1 to hit for bow specialists at short range is in place of, not in addition to, the +2 at point-blank range (i.e. if the target is at point-blank range (6-30'), the bow specialists gets +2 to hit and damage and does double damage; if he's outside of point-blank range but still within short range the bow specialist gets +1 to hit and no damage bonus; if he's at medium or long range the bow specialist gets no bonus to hit or damage)
Since he's only 11th level, not 13th, he only gets 3 attacks per round, not 4
So we're looking at 9 attacks per segment, x 3 segments, assuming each one hits for max damage (19) = 513 damage.
However, since he's an elf, he could potentially get 4 segments of surprise instead of 3, so for the 4th segment we can tack on potentially another 171 points of damage , bringing the grand total up to 684. Not quite 900, but still not too shabby!
Make him a human instead of an elf and we lose that extra surprise segment and +1 to hit (which doesn't much matter since we're assuming every attack hits anyway) but then you can get the 18/00 strength and 13th level, giving 1 extra attack per round (i.e. 3 more attacks per surprise segment) and +3 additional damage on each one, which kicks to total up to a whopping 792.