Depends on your budget. That being said no matter your budget avoid the Blue Yeti & Blue Snowball.
As for specific recommendations these are the best in their respective price tiers. Prices fluctuate so don't buy they outside of the listed price ranges, you will be overpaying.
Hentai's General Mic Recommendations
Logitech USB Dynamic Rockband Mic ($10-20)
CAD U37 USB Condenser Microphone ($40-50)
Behringer C-1U USB Condenser Microphone ($45-60)
Audio-Technica ATR2500 USB Microphone ($50-70)
MXL 006 USB Condenser Microphone ($70-100)
Monoprice USB Condenser Microphone (<$100) *
note*
MXL 008 USB Condenser Microphone ($100-130)
Audio-Technica AT2020 USB Plus Microphone ($100-130)
* - Note: The Monoprice USB Condenser Mic is basically a MXL770 ($85, analog) with a built in audio interface and without the hard case+shockmount.
Below the $50 territory you start entering the Rockband mic range and I recommend against making any significant investments in this price range and instead saving your money. Above the $130 price range you start seeing significant diminishing returns, the selection of USB mics decreases, and you are better off going with an Analog Mic+Digital Interface route, rather than buying a USB mic.
Example: At $140 you can get a
Blue Icicle ($35-40) audio interface and an analog
Audio-Technica AT2020 ($85-$100, analog) for just $10 more than its USB counterpart. Advantage of getting USB and microphone elements separately being you can update them separately as needed, can have multiple analog mics, get access to the healthy used analog mic marketplace, and gain access to a wider selection of analog microphones.
Caveat: While I used the analog AT2020 in my example, if I had to choose between $100 condenser microphones I would have gone with the
Behringer B-1 ($100, analog) or a used, normally more expensive analog microphone off of eBay or Craigslist. Also in order to cut on costs I purposely excluded the cost of a 3" or 6" foot patch cable. While AT2020/B-1 + Blue Icicle would work without it I recommend against running it in that configuration. Get a
3-foot or
6-foot Balanced/Shielded XLR cable for <$8.