I like Legato and Mithos the best, since those are words that actually exist in real life. I get the feeling Seifer Almasay is going to win this poll, because Final Fantasy, but personally, I think Mithos Yggdrasil is pimp as fuck. I'm surprised there's so little support on this forum, populated by nerds, for an entertainment website called "The Escapist," for changing your identity in some small way. You do your thing, Whatislove, and let the haters hate.
Full disclosure, though: I feel like another reason most people are voting for Seifer Almasay is becuase it is the least likely name to get you punched in the dick. Seriously: even when I see "Darth Something" or "Vegeta[seriesofnumbers]" names on the Internets, where anything goes, I want to punch people. I don't know how much worse it would be in real life. There's something very juvenile about these names that just makes me sigh in exasperation. Regardless of how interseting a character Vegeta was or wasn't or how cool sith lords are or aren't, I feel like the other three are slightly more appropriate names for a grown man who isn't an angsty tween who secretly wants to be able to explode planets or kill people with their dark force powers and emo poetry. Still, Seifer and Kaiba both also kind of have that problem to a lesser extent...
You know what, fuck it. I'm voting for Mithos Yggdrasil twice. That's 4 points, right? It's an awesome name with ties to genuine mythology as well as pop culture, and that makes it much more respectable. If someone introduced themselves to me as Mithos Yggdrasil I would be thinking "That's weird, but also kind of awesome." If someone introduced themselves to me as any of those other four names, I'd be thinking "Oh God, how can I get out of this conversation?"
... as an aside, as an American, I kind of feel like the fact that OP is Australian factors into his laid back, cavalier, entirely reasonable attitude about this whole thing.