I like Monte Cook's "Mage Blade" core class from Arcana Unearthed/Arcana Evolved.
The only gripes I have about it are minor; 1, it's Charisma-based despite being described as a trained spellcaster and warrior, not just a natural-born sorcerer-type; 2, its skill points and class skills kinda suck, which compounds the annoying focus on Charisma instead of Intelligence.
So it's a very skills-poor warrior-mage, but fairly solid in its warrior-mage role at least. A melee weapon they bond with and enchant slightly for free (just enhancement bonuses to attack and damage, but they're free), the ability to use that weapon for somatic spell components and avoid ASF from armor/shields that way, an ability to magically shield themselves on occasion, a few bonus feats over time, bard-like spellcasting progression (but up to 7th-level spells at the end), and a bit of magic-parrying and magic-defense-piercing with the bonded weapon at upper levels.
Well, I'm kinda irked that they suck a bit at 1st-level (like a bard...), but they definitely get better after the first few levels (and most spellcasters or hybrid casters kinda suck for the first few levels, anyhow).
Eldritch Knight is kinda strong I guess, but only after the first few levels (it isn't until 3rd or 4th level at least, that they start to clearly outmatch a fighter/wizard). But it's terribly bland and dull, not even an interesting skill list or the like. Overall, really, a cleric or druid makes a better melee combatant than an eldritch knight. A druid or pure wizard makes for a better ranged combatant, too. Also, the PrC takes too long to reach (7th level at least).
The Spellsword is kind of decent, but not as good in 3.5 and was never really quite effective enough. It is more interesting than the EK, though.
The Shadow Knight from the EverQuest RPG (it's OGL and heavily d20-based, but no d20 STL use because it has its own XP chart and such) is fairly compatible and fairly good, but kind of evilish and very necromantic in terms of its magic abilities.
The Duskblade from Player's Handbook II is a solid warrior-mage type, but overpowered in my opinion and just plain broken. They can be fine sometimes, at low levels, but Arcane Channeling is poorly detailed and potentially very broken. They get a ton of benefits at 1st-level and such, and a whole ton of spell slots as they go up in levels. Tons of swift-action spells and the ability to quick-cast some of their other spells as swift actions whenever it's convenient.
They have a full Base Attack Bonus, a cleric's d8 Hit Dice, two strong saving throws, a bonus to overcome SR after they've hit someone in melee, and the ability to cast freely with most armors and shields. They're basically an arcane cleric with more fighting ability (at least, without needing to cast a bunch of spells before each fight) and more hard-hitting and defense capacity, but no access to 6th, 7th, 8th, or 9th level spells. That would be fine if the only classes in use were Duskblade, Cleric, and Druid, but they're not....
Swordsages are the best warrior-mage class that isn't actually a spellcaster. ^_^