Like Jay, I have a whole plethora of Bibles at hand, but tend to use the NKJV for general reading, and the KJV for quotations, since more people will "recognize" a quote from that one than they will any other reference. I have a new KJV-ER, Study Bible, published by Whitaker House, which I like VERY much as well. It has a number of nice hard-copy features, such as complete references for the "Hebrew Names of God" in each use ("YHVH Elohenu", YHVH t'tzivenu, etc.) and "Enhanced Readability", which means all the "thees" and "thous" have been swapped for "you"s, and the '-eth' endings are updated. ("He chasteneth" becomes "He chastens".)
If I had to pick an "only" Bible in hard copy, however, it might (for now) be that one, or The Scriptures, which is a generally good version that avoids the "God" and "the LORD" issues of name-replacement by putting in the actual Hebrew, which I prefer anyway. Kinda neat.
I still have a large edition original 1599 Geneva Bible copy, complete with the historic margin notes, that I use for the occasional, inevitable, "KJV is the ONLY Inspired Word" debates. (The Geneva is better in every respect, I contend, when "push comes to shove", and the differences are VERY instructive!)
I also find the electronic versions VERY handy for articles and research. While I'm still climbing the 'learning curve' on e-sword (and have as many of the free versions as I can get my hands on), I tend to use the BlueLetterBible.com a LOT when I'm on-line. And on THAT one the KJV is the obvious choice. Here's my reasoning:
When I do a text search, the trick is always to remember the EXACT words that are used in a line. Even though the NKJV, for example, may be close, the differences can make a search turn up empty.
(let's see, was that word "chastens", or "rebukes"...?)
The KJV will be free on any system or tool you find, and it will be available on any computer you sit down at, whether it's a friend asking a question, or a library, SOMEWHERE or other. If you ever have a "does God REALLY say that about marriage?" issue, when your own highlighted text is not at hand, can you find the quote you want?
Blessings,
Mark
PS> I hope to get my hands on a new translation, from sets of relatively recently available ancient texts (including older-than-the-Greek versions of Matthew, John, Acts, Revelation, and many of the letters) within a few days. I'm still looking through an e-draft of the translation; quite interesting.