Currently, I use Sanford's Uniball Micro. I got a pack of 24 at Costco for about $10 (I don't remember the exact price). I like it because it's great and cheap.
If you're looking for ballpoint ones, I used to like Pentel's RSVP. However, the pen seems to die out a lot faster than the ink shows. If you look at my history notes, you can see the color slowly fades away. I'm not exactly sure what happen, and it took me 2 pens to find the pattern. So I decided to go with the Uniball. Maybe I'll give it a try again after my Uniball dies out...