Finding a pen is like searching for a violin bow: you need not only find a tool that feels good in your hand, but also one which helps you express yourself.

Go to a local pen shop--one which still advertises that they repair old fountain pens and deals in antique pens. Ask questions (repair history, general background, etc) and write with pens from a number of manufacturers and ages. You'll find what feels good.

Also keep in mind that different pens have different uses:

Fountain pens are great for focused writing, but are only sometimes manageable for general paperwork (and impossible to use on multipart forms!). They flow effortlessly on good paper, but the nibs clog up on sub-20lb bond paper. I happen to like Parker and Waterman, but others like Omas and some (despite poorly manufactured threading on their screw-on nibs) like Mont Blanc. The old Parker Sonnet (before the large gold band) was a joy to write with for long periods. Just keep in mind that fountain pens take a while to get used to: they changed my handwriting from unreadble chickenscratch to elegant and stylistic scrawl in a couple of months. (I'm working on getting it to simply elegant, but I tend to code too much for that to happen).

Rollerballs get some of the flow of a fountain pen, and they do give you some flexibility on which papers you can use it on. I liked the Waterman Expert: thick, light, and stubby.

Ballpoints: well, they are good for multipart forms. Some (like the Uniballs) are good pens for simple everyday uses where you just don't want to whip out your pen. Like around those people you tend to walk away with your pens....

Ultimately, your choice is up to what feels good in your hand and what uses you intend to use the pen for. You may need more than one pen.