Link: Fighter-20: The "Gatling Chain Gun" Tripper by Snow Savant
http://boards1.wizards.com/showthread.php?t=163005
And my own advice.
Race:
*You will need many feats to pull this off. That makes being a human attractive.
*Large size is also a big advantage because it increases your reach. If your DM will let you be something that's large for LA +1 or +2, go for it.
*This build is somewhat appropriate for a dwarf, but dwarves benefit most from wearing heavy armor and moving slow. Chain wielders need high dexterity, which means you don't want to be in heavy armor. Your call.
Ability Scores:
*You want Dex to be at least 14 if not 16. Why? So that you can use combat reflexes to good effect.
*Str should be 14 if possible. This boosts your trip checks and does x1.5 damage (the chain is a two handed weapon).
*Secondary Stats: Wisdom and Con. Every fighter needs con. And don't dump wisdom if you can avoid itas you will have a bad enough will save.
*Tertiary Stats: Int and Cha. Int needs to be at least 13, so you can't totally dump it, but don't pump it much higher than that. Cha can be dumped.
Feats:
First,
combat expertise and
improved trip are essential. Take them at first level.
Combat Reflexes is also essential. You need to control a large area perhaps even while flatfooted, so get this ASAP.
Exotic Weapon Prof: Spiked Chain can wait a bit. Until you are proficient, I'd suggest using a reach polearm such as a guisarme backed up with a close-in melee weapon.
At this point you have some options. I don't think Improved Disarm is worth it, but if you're fighting lots of humanoids, it might be. I generally also do not think that Improved Feint is very worthwhile. However, if you have a high bluff skill, it might be, merely because your trip attacks are then basically against AC 10 (touch attacks ignore armor and shield, feinting negates their dexterity bonus) so you should always hit.
Dodge-->Mobiltiy-->Spring Attack is attractive, especially because you can then pick up Whirlwind attack. If I went the Spring Attack Route, I would be heavily tempted to multiclass (maybe a level or two of rogue or even a spellcaster class) to increase my utility... Spring Attackers only make one attack per round so BAB doesn't matter as much, and you are less vulnerable to enemy attackers so you can lose a few HP and still be ok.
Power Attack is also fun. The chain is a two-handed weapon so you get to trade your to hit points in for 2 damage each. And combined with Improved Trip, it's deadly -- you get +4 to hit prone opponents! Also, power attack gives you an option vs. non-humanoid opponents. You can always whip out your greatsword and start doing massive damage against that non-trippable dragon or elephant or demon!
If you can, pick up Iron Will. This is a good feat for any fighter-type: Have you seen your will save?
If your Dex ends up being four or more points higher than your Str, Weapon Finesse is a good bet. This also reduces your magic-item dependency: Instead of a Belt of Giant Str +4 and Gloves of Dex +4, you just need the latter... Then again, your str checks to trip don't get helped by it either.
Multiclassing
I think rogue synergizes nicely with a chain wielder, especially with a 2 level dip to get evasion. You've got high intelligence, so you can keep your Search and Disable Device checks up throughout your career. You've got high dex, so your reflex save is good and you'll probably make your evasion check. Getting a few ranks in Use Magic Device, multiclassing to wizard, or taking a few level of a cleric type with the str domain is also handy so you can use scrolls and wands of enlarge person -- they're much cheaper than potions.
Have fun!