Dervish
The dervish PrC has many special abilities that are allowable only in light armor. I am currently playing a elven fighter/dervish that uses a faclhion (2 handed slashing weapon) as opposed to something lighter and he is very effective in combat.
The dervish gets a to treat scimitars as light weapons for use in TWF and Finesse. I instead opted for the big two-handed version (a falchion isn't actually the two-handed scimitar it is described as in DnD, it is a one-handed europeon weapon more like a cleaver, but I will play it that way if they say so...).
The prerequesite for the class is specialization in any slashing weapon (grab your greataxe..), you get a special ability with the scimitar, but don't have to use it.
Using a large slashing weapon with the class allows for some deadly cominations (derish dance gives plusses to hit and damage, combine this with power attack for a two-handed weapon and he fachions great critical rang and you have a very potent offense) and most of the special abilities require light armor; you get a bonus to AC to make up for this too, by the way.
All in all, from my experience the derish, which is designed for light amor, works really well with large two-handed weapons.
pbd