Generic Classes can be found here: www.d20srd.org/srd/variant/classes/gener...
I believe the general principle here is to get bonus damage, lots of attacks, and flat-footed generators. Underfoot Combat and Confound the Big Folk both work well with a Dervish Dance, for example. You can have a blast rolling around and running under bigger dudes.
A few Potions of Reduce Person help a lot. But yeah, what's your starting level? You didn't give nearly enough information to be very helpful.
link is in the handy link tool thread
Completing the picture: As a swordsage, you have tumble as a skill and tons of standard action "strike" (as they're called) maneuvers, so making a mobile skirmisher is quite easy, you won't need to full attack really. If you still want to, the Sudden Leap boost (swift to get a free jump check) and Pouncing Charge (full round action to...charge and full attack, obviously) maneuver can help, anyway. At low levels, the Child of Shadow stance, which gives you 20% concealment for one round after you move 10 or more feet, provides even more awesome synergy.
If you can, get a spiked chain (by that I mean, the Exotic Weapon Proficiency), so even though you're small, you have better reach than a human.
As a swordsage, you can get free Weapon Focus on it.Replacing Str with Dex: Weapon Finesse obviously. As a swordsage, you can easily qualify for Shadow Blade, which lets you use Dex for melee damage with certain weapons. And my favorite low cost magic item is the Boots of Agile Leaping from Magic Item Compendium. For 600 gp, you can replace str with dex on jump checks and even better... if you have 5 or more Balance ranks, you can stand from prone as a swift action and not provoke attacks of opportunity. At that low price, it's well worth paying +50% (900 gp total) to attach it to your boots of striding and springing.
One final note, the level 3 maneuver "Soaring Raptor Strike" has very very good damage for the level you can obtain it (character level 5+) -- regular melee damage +6d6 -- but is handicapped in two ways. One is you need to beat the foe's AC with a jump check (treat it as the jump DC), the other is that you can only use it on enemies larger sized than you. As a small creature with speed 30 (ie, no jump penalty for speed), you can reliably use it on almost anything you'll fight.
I want to build a fighter of small size that can deal lods of damage and be able to take it as well or at least avoid it.
If you want really underestimated (and small was a generic term, rather than the size category), you could go for a charisma based Petal character who focuses on the various "must be smaller than the enemy" feats and special abilities. Nothing says harmless and inoffensive like a Tiny little winged fairy who specializes in collecting nectar from flowers.
Between the flight and very nice stat bonuses though, they make for one of the most playable Tiny races in the game. if i remember the build its
Carmadine Monk 2 / Swashbuckler 3/ Blade Bravado 10 / xxx 5
CAramdine Monk can be replaced with Kungfu Genise and regular monk.
i think the one time a few years ago i played this style build i put 5 levels in physic warrior at the end so i could drop myself down 2 size catagories to add to an even more nuts AC and i had some one casting fell the greatest foe on me so i got more sneak attack damage.
what was fun was adding robilars gambit in at the end of the campaign. if you are starting at first level the build is fun to play even at the begining. its not a build you have to play at 20th to enjoy or at least i didnt need to
The Other Killer Gnome build, referred up above as the "I'm Tiny but You're Dead" build, is a classic small fighter gnome based build. The Dodge AC it builds up is incredible.
==Aelryinth