3-foobar2000 (Windows)

foobar2000 is one of the most flexible, customizable, and tweakable music players available, and it doesn't shy away from that fact. foobar2000 calls itself an "advanced" freeware audio player, largely because it's lightweight, can play virtually anything you throw at it, and while it's powerful and flexible, it can be a little daunting to get used to at first. More than a few people have given up on foobar because they'd rather spend more time listening to their music than tweaking their media player, but if you're the type who wants a personalized listening experience and a tool with just the tools you like (and none of the bloat you hate), foobar2000 is worth a look. The learning curve isn't as steep as some people make it out to be. It does all the things you would expect from a media player: It supports gapless playback, has tons of customizable hotkeys to control playback, supports CDs and crazy file types, and more. Perhaps most interestingly, foobar2000 supports ReplayGain, which does an amazing job of making sure your music is all played at the same relative volume and loudness. Those of you who called out foobar2000 almost all rallied to the fact that it's extremely light on system resources, well-developed, and has a wealth of plug-ins and add-ons that extend its functionality. Many of you mentioned that it supports incredibly rare file formats, and it can handle massive music libraries without choking. It's completely free. If you're the type of person who likes to start from scratch and build essentially the ultimate music player that's just right for you, foobar2000 will get you there, and you'll be happy with the end product.