It really depends on what you prefer, though I would stick with one of the major browsers including Internet Explorer (NOT v6), Firefox, Chrome, Opera or Safari. I personally prefer Firefox, but also use Chrome and IE on occasion for specific reasons (website compatibility testing, etc).
Firefix is my favorite, but there are some sites that cannot be used in Firefox. Internet Explorer has copied a lot of what made Firefox the best, so its typically an issue of what you are comfortable with. ( I don't use Apple so I have no clue on Safari)