RE: Dwarf Fortress, Tarn "Toady One" Adams basically made it known on his forums that he'd work on porting DF when KQ was ported, reason being that they share much fundamental code.
One of the things I love about Mac gaming is the way the lack of selection forces me to seek out tiny, poorly publicized games I've never heard of.
Millenipede is one of those. Likely the most beautiful recreation of 'Pede ever spawned. And then there's
Titan Attacks, a really polished, jazzy Space Invaders descendant.
Xiq is another. It's like Qix, but you shoot lines instead of making them by moving and there's not one big, slow enemy, but a neverending onslaught. Plus customizable music. Definitely innovative.
I have to agree with all previous posts in that I can't think of any OS X-exclusive titles that're worth more than fifteen minutes of play, but I think exclusivity is a poor benchmark anyhow. So without further ado, on to the usual suspects.
The same
guy who ported most of Cho's games also ported a slew by Junpei Isshiki.
Numerous roguelikes in several variations each have been ported to the Mac. Scads of Angband variants, mostly, but also Nethack, ADoM, ToME, Moria, and Crawl.
Speaking of Crawl, Henzell's Overgod and Garden of Colored Lights were ported. Can't remember where I found them, but a little google-fu and you should have them.
Jon Mak's Gate88 is compatible, as is Marco Incitti's Gridwars.
Several of
Retrospec's releases are OS X-compatible, including Head Over Heels and Wizball.
And, well, lotsa stuff is cross compatible. Lots. Kiki the Nanobot, Facade, BZFlag, Escape Velocity, Jet Set Willy, Mutant Storm, N, Super DX-Ball, Super Mario War, numerous ports of Ultimas, and then there are all of LittleWing's fabulous pinball games. People talk about Macs not being any fun, but I've never lacked.