That depends where you are, how close you are to the broadcast antennas, and what kind of line of sight you have.
I'm on the western shoulder of Capitol Hill, roughly due east of the Queen Anne towers and north of the Madison towers. I tried a couple of amplified (plug-in) rabbit-ear-plus-dish type things and could not get a consistent signal. Turns out I was exacerbating what amounted to a signal echo chamber.
So I went lower power and got this guy, and as cheesy as it looks, it works like a champ:
http://www.meritline.com/artec-an1-digital-flat-tv-antenna---p-31475.aspx
PBS and Fox/JoeTV/Antenna TV come in fine from the Madison towers, and I get KOMO, KING, KIRO, the CW, KONG, and some Asian channels (44-x) from the QA towers.