Ok, I'm looking at getting a good mic to use while gaming and for recording music (guitar mostly). My budget is anything less that $100, but preferably less than $75. It doesn't have to be a headset since I like using my sound system for my PC, I just need a good quality mic that sounds good and has good tone balance. It can be a desktop mic, a headset, an earpiece, whatever, just as long as it has good recording quality and allows me to use my speakers as the default audio out.

I'm partial to http://www.sweetwater.com/store/detail/C01UCW/, but Iv'e never used this particular model before. I had a smaller travel usb mic for years and it was solid quality sound (not really "studio" quality though), and paired with Audacity I was a happy camper. My first mic was a Blue, but I forget what the model was. It was cheap ($15) but did a great job for what it was. I did mostly sfx, voice recording for mods, and Skype.

That would be exactly what I need for recording, but I think it'd be a bit hard to use for gaming?

I was thinking more of a headset that you could bypass the headphones on and just use the mic, or a desktop mic with a stand.

get a Shure C606, they're brilliant as well as brilliantly cheap. You'll want a mic stand though.