Mac only: Media libraries like iTunes are great, but sometimes it just feels limited. Enter Instinctiv, a music player with taste-learning shuffling and non-iPod device syncing powers.
With so few music players for the Mac out there, every time a new one comes on the scene we're intrigued. Through Instinctiv, you can browse your iTunes library easily (and with some nice eye candy to boot), but Instinctiv's raison d'être is its Genius-like shuffling powers. Not only can you pick a song and say "play more songs like this", but it also has its own, intelligent "Instinctiv shuffling" feature. Instinctiv shuffling takes your listening habits (that it learns with every time you use the program) — including what songs you play more often, what you skip, and other such things — to play music that it thinks you'll like. Instinctiv also has one of the simplest concert-watching features ever, showing a list of artists in your library coming to your area, in chronological order of concert date.
Oddly enough, despite it being a completely native Mac app (unlike iTunes), it takes up just as much RAM as iTunes, and its CPU usage fluctuates like crazy (from 2 per cent up to 95 per cent and back again). However, it is still at the experimental stage, so we don't want to judge the app on these shortcomings quite yet. An increase in resource efficiency in the final version, though, would make this a truly awesome program. Note that despite these statistics, I haven't noticed the kind of slowdowns and crashes that I often do with iTunes, so it's certainly still worth a look just for its cool features.
Instinctiv is a free download, Mac only (though the development team is working on apps for a number of smartphones).