Are you moderately to incredibly affluent? Then chances are high that you own a Macintosh computer. There is a slimmer chance beyond this that you have installed Boot Camp and thus Windows on your Macintosh computer, in turn allowing you to play whatever PC games you so wish. More likely you think it too complicated by half, or are like the guy who visibly recoiled, started shaking in fury/grief and needed consolation from his girlfriend upon seeing Windows running on my own Macbook.* Apple people. Whatever the reason you don't also have Windows on your Mac, you might be happy to hear that Ncsoft's jolly good subscription-free MMO Guild Wars 2 has just released a beta client for Macintosh computers.
Word is the Mac version accesses the same servers as the PC version, so you don't need to worry about being whisked off to a separate universe, and if you own a Mac and PC in some form (or, again, a Mac with Boot Camp) and have bought the game, you can access either or both versions. Just like WoW, basically. Arenanet have used TransGaming's Cider tech, which means it's a sort of Windows translation rather than a native client per se. I believe when employed carefully this means no meaningful performance hit, but I am quite sure comments will lead to a more fulsome discussion of the issues around this. One definite boon of it is that all updates will be simultaneously available on both platforms.
You can get the OSX client by logging into your GW2 account management page, and there's an FAQ about this whole posh PC shebang right here. Here's the system requirements, for people who don't rush out to buy the latest model every year to ascertain whether the MMO will run on their Jobsmachine.
Mac OSX 10.7.X or later
Intel Core i5 or better
4 GB Ram or better
NVIDIA GeForce 320M, ATI Radeon HD 6630M, Intel HD 3000 or better
25 GB available HDD space
That means it will run on my Macbook Air*, though whenever I run any 3D games on that its fans become loud enough to deafen the dead and its base hot enough to flay the skin from my genitals. That's why I mostly only play the Binding of Isaac and Avernum on it. I wish I'd bought a different laptop :(
Anyway! Hopefully you have something meatier, but do dear in mind the current OSX client is billed as a beta - so if you hit issues they might well be resolved in the 'final' version, as and when that crops us.
* Hey, don't look at me like that: it's tax deductible when you're self-employed.