Pentel energel 0.5mm needle tip
Really smooth flow, retractable, deep color, does not smear. I am the kind of lefty where almost everything smears and this bad boy does the trick. Took me actively searching for roughly 6 months before I found it. I will never go back to any other type of pen ever again (assuming they continue to make it).
http://www.staples.com/product_PENBLN75A?externalize=certona
You can find boxes of them for cheaper at other places like ebay and amazon (at least I have in the past); same with finding different colors.
Runner up would be the uniball micro 207 (0.5mm)
Again retractable, decent color and does not smear. But it definitely is not as smooth as the pentel. On some types of paper the micro tip tends to almost get caught or scratchy feeling. The 0.7 bleeds too much for me and the 0.38 tends to be too precise that it gets scratchy on most paper. The 0.5mm tends to be a happy middle ground but still way behind the pentel. Cost wise I think its cheaper than the pentel so that might make this more favorable for your situation.
http://www.staples.com/uni-ball-207-Retractable-Gel-Ink-Pens-Micro-Point-Black-Dozen/product_598808
**Again I am sure you can find cheaper deals elsewhere, I am just providing the link so you know what I am talking about haha.