I'll add a couple to this list:
Vanguard
Luminary
Both carry a connotation of "elite", and Vanguard also essentially means "leading from the front" - something that can definitely be attributed to arcane warriors.
The problem, like with many other gish concepts and names, is that they are also lacking in real-world inspiration of any sort. Granted, so is "fighter", but it sort of has to be.
These are great names too. I especially like "Vanguard" because it has a connotation from Mass Effect -- the fighter/mage hybrid in that game was the Vanguard, and their signature ability was a sort of charge/teleport reminiscent of the swordmage's Aegis ability (from 4E). They "led from the front" in the sense that they could close to melee rapidly because of their biotics.
"Luminary" is a pretty cool word too -- I'd put it in the same category as "Magus" or "Thaumaturge" in that it sounds more magical than warriory.
I'll also join the growing chorus that Argonaut isn't a great name for a base class. I'll generalize this and say that anything which is a proper noun is probably not a great concept for a base class. It might work for a subclass, though. "Myrmidon" is also a cool word for a subclass.
Now I am thinking about some sort "Epic Hero" class with subclasses from mythology like "Argonaut," "Myrmidon," "Amazon," "Berserker," etc.