What are your must-have apps?
makecheck: 1. A text editor that is powerful, stable, and basically good for programming.  I rely on "vim" almost always, but Xcode is a nice fallback.2. A powerful terminal.  On Linux, "aterm" is the best I have ever found.  On Mac, I prefer MacTelnet but Apple's Terminal is pretty good.3. A suite of infrastructure tools.  I've been in the Unix universe for many years, so it's hard to imagine anything except the usual suspects: ls, find, grep, awk, xargs, etc. all joined through shells, Perl and Python.  These are definitely "must have"; even if they don't qualify as a single app, they certainly qualify as a single entity I couldn't live without.  (And having stumbled my way through Windows' inadequacies, I now know this painfully well.)4. A web browser, and by extension, Google.  I like OmniWeb the most, though I use Firefox at work.  I've even been known to use Lynx, or the occasional automation through "wget".  There is simply no faster way to get information anymore; I'm more likely to web search for tools than run "man" pages, even.5. E-mail.  I prefer a trivial "send" interface (I like basic command line "mail" sometimes, though "pine"/"alpine" are my favorite).  I do use Thunderbird and Apple's Mail quite a bit.  I am not a fan of overly complex tools, but the ability to tag and search/filter mail by tag is a really compelling Thunderbird feature.