Warblades are one of the three base classes in Tome of Battle. They are basically a better version of the Fighter class, though most experienced players would argue that was never a particularly good class in the first place.
Where the Fighter PC class gets bonus feats every other level allowing you to customize it to your whim, the Warblade gets a much smaller selection of bonus feats, but in return gets better skills, use of the Fightan Magic, Uncanny Dodge, and some class skills which really benefit from decent intelligence scores (therefore more skill points) and make the class more versatile out of combat (though they lack the class skills to replace Rogue). These bonuses work on a variety of things such as confirming critical hits, extra damage while flanking or sneaking, more accuracy on attacks of opportunity and insight bonuses on most combat tricks like bull rushing, tripping or disarming opponents.
Put together with the addition of the choice of stances and maneuvers means you get a much more versatile combatant than most other PCs. Even if you don't want to take the class to its full progression, it works really well as a filler level for any PC that fancies gaining some combat clout: One/two levels of Warblade offers considerably more than just one/two levels of Fighter, since the low level stances often remain effective no matter what your primary class is and Weapon Aptitude means you can pick up and use just about any piece of equipment as if it were your primary weapon, too. All of a Warblade's disciplines are officially non-magical. This generally doesn't raise too many eyebrows, with the sole exception of Iron heart surge, which is notorious enough to have its own page.
One of the most interesting things about this class outside of maneuvers is the Weapon Aptitude feature it gets at level 1. In addition to counting your Warblade levels as a Fighter levels (albeit at -2) allowing them to get those (generally meh) exclusive feats (like weapon specialization), it also lets you change the weapon designation you have on already selected feats. So if you had Weapon Focus (Greatsword) you could change it to Focus (Longsword) the next day. It even works on Exotic Weapon Proficiency, meaning you never ever have to suffer from non-proficiency penalties. This means they'll never be victim of being unable to use a randomly generated weapon. More controversially, the ability is worded so it allows you to "change the designated weapon for any feat you have that applies only to a single weapon (such as Weapon Focus).", which RAW can be argued to allow changing the designated weapon for feats that never gave you a choice of weapon in the first place, such as the weapon style feats from Complete Warrior.
Warblade is generally considered Tier 3. They're really good at smashing things, and the maneuvers give them enough versatility to deal with encounters where raw smashing struggles to be useful. Their naturally high skills can make them useful out of combat as well, though they aren't the greatest here.
There's an Arcana Unearthed parallel: the Warmain. Because even Monte knew he couldn't have his party's fighters sitting in the cuckshed watching the magic-users have all the fun.