My personal favorite Linux applications for everyday use:
Internet Browser: Firefox
I use firefox primarily, but still keep chromium around in case the one problem I still have with chrome gets resolved. For some reason I can open a million tabs in firefox and have no noticeable impact on my processor. Conversely chromium starts really weighing down my processor after opening just a couple tabs. I dunno why, but if they fix it in the future I'll consider using chromium rather than firefox.
Oh, and on that here's a tip that I've found incredibly useful. When you have more than one browser installed and you open up your non-default browser, it will usually ask you if you want to make it your default. Check the box that says "don't ask again" or however it's phrased, and then don't make it your default. Do that with all your browsers and then whether you open up firefox or chromium neither will nag you about not being default. Huzzah.
For media player, I've got a couple standby Linux players that I usually go to. For watching video, VLC is in my opinion far better than the others. It can play just about any type of video, has nifty filter effects (if you're so inclined), can up the volume of the source to 400%, has the ability to make playlists, shuffle, repeat, blah blah blah. Basically it's just pretty great.
As far as music goes, it sort of depends on the size of your library. I used to have more than 20,000 songs and trying to use Banshee or Exaile was just obnoxious. Banshee would be very slow to respond when scrolling through the entire library playlist, or when scrolling through large (>5000 songs) playlists, or when changing songs. Basically in many different aspects it was slow. Also it had a tendency to duplicate songs, and then duplicate the duplicates, and so on and so on and so on until 20,000 songs is more like 24,000 when you include all the duplicates. And it's just not easy to get rid of them all. Exaile had a similar problem with lagging, and with randomly closing when trying to import everything. So basically unless you've got a pretty small music library those don't work too hot.
I ended up deleting everything and just starting a new music library, so I suppose I could go back to using Banshee or Exaile, but I'd rather not.
Instead I prefer organising my music by hand (music folder, artist folder, album folder) and adding whatever I want to audacious. The default skin for audacious is really ugly but if you liked Winamp on Windows XP then you'll dig it because Audacious can use any Winamp 2.x skin (of which there are some very cool ones).
To manage a large library, there's still not really a good FOSS solution but you can use Foobar2000 and Wine, and it works just fine.
I think empathy works just fine for instant messaging; the fact that you can be on facebook chat while not actually being on facebook tends to be mind-blowing to non-technical but still facebook-using people.
For a wallpaper changer, I recommend desktopnova, it's got a really low footprint, you can change in intervals and it's pretty easy to use. Doesn't get all snarled up when it's source folder has hundreds of images (unlike wally, which while being a very versatile program tends to use a lot of processor power and freeze things momentarily when switching wallpapers).
My favorite bittorrent client is Deluge, for it's relative simplicity, it's customisability, speed, and just general ease of use. Also you can send yourself an email when a torrent finishes downloading so if you're away from your computer you can still check your email to see if torrents have finished. Cool.
To enable corner actions I use Brightside, which I do not know any other similar programs. You can set the action to start screensaver, prevent screensaver from starting, lock screen, or a custom action like gnome-terminal or update-manager (the terminal command is pretty awesome actually).
More to come another day!