I did some testing with 2 of my characters (Item and R) in PvP to see what two-handed weapons give the longest range (for trying to melee the Demon Queen for instance).
My results:
Totemic Staff of Splinterskull looks much shorter but has same range as Rahl's Might.
Assumption: all weapons of the same type have the same range.
Item's Human-sized Rahl's Might looks much shorter than R's Halfling-sized Rahl's Might, but they have the same range.
Assumption: character's size does not affect range
I ranged-in where each weapon stopped hitting, and found the distance with /loc:
Standing:
Greataxe and Maul: longest range THF
Animations 1-4 hit out to 2.71
Animations 1, 2, and 4 hit out to 2.95
Animations 2 and 4 hit out to 3.03
Quarterstaff: 2nd longest range THF (96.3% of Greataxe)
Animations 1-4 hit out to 2.61
Animation 4 hits out to 2.86
Falchion, Greatclub, and Greatsword: shortest range THF (94.1% of Greataxe)
Animations 1-4 hit out to 2.55
One-handed weapons, single wield (Dagger to Bastard Sword): short range (94.1% of Greataxe)
Animations 1, 2, and 4 hit out to 2.55
Animation 3 hits out to 3.04
Unarmed non-Monk or uncentered Monk: very short range (74.2-76.4% of Greataxe)
Animations 1-2 hit out to 2.01-2.07 (didn't range it in exactly)
Animation 3 hits out to 2.40-2.64 (didn't range it in exactly)
Unarmed centered Monk (thanks to Artilleriae for testing): Longest range standing attack (109-115% of Greataxe)
All animations hit out to 2.94-3.12 (didn't range it in exactly)
Need to add Standing Dual-Wielding measurements. Seemed much shorter than Standing Single-Wielding.
Moving:
Falchion, Greataxe, Greatclub, Greatsword, and Maul: same long range while moving
Animations 1-2 hit out to 5.44
Quarterstaff and all 1-handed weapons (Dagger to Bastard Sword single wield or main-hand): same fairly long range (92.8% of Greataxe/et al)
Animations 1-2 hit out to 5.05
Off-hand weapon (Dagger to Bastard Sword): medium range (81.6% of Greataxe/et al)
Only hits on Animation 2, hit out to 4.44
Unarmed non-Monk or uncentered Monk: short range (68.9-71.3% of Greataxe/et al)
Animations 1-2 hit out to between 3.75 and 3.88 (didn't range it in exactly)
Unarmed centered Monk (thanks to Artilleriae for testing): Shortest range moving attack (42.1-50.5% of Greataxe/et al)
All animations hit out to 2.29-2.75 (didn't range it in exactly)
Monks, use your Kamas for fighting on the run!