Text/Code Editor: Notepad++
This random little open source text/code editor is the best I have ever used, including paid suites. It has support for more coding languages than I knew existed. As you would expect it understands the language and uses colors to denote different types of code. The search search/replace function is to die for -- more options that I know what to do with -- and the file management (tabs included) is great for cleaning up your taskbar and increasing productivity. You can even save a link file that includes which files you have open, that way if you're working on a set of code with say, 10 separate files, you can open that one link and viola, all of your relevant files are open. The only language that I have encountered that is not supported by Notepad++ is ADPL, the Ansys programming language based on Fortran. If anyone knows of an add-in I would appreciate it.
Video Player: VLC
If you don't know about VLC you are probably new to the interwebs or computing in general. It is the benchmark by which all other video players are rated. The only file formats that it does not support are moronic proprietary ones that aren't mainstream - or good - anyway. It has a bare bones interface packed with every option and feature you could think of. Keyboard shortcuts make manipulating the video on the fly simple and actually useful. Croping and changing the aspect ratio on those videos where the author fancies
If you have a windows logo in the top right corner of your browser (read: IE) you should be ashamed.
File Compression: Winrar
Winrar has been a favorite of mine for many many years now. I migrated from Winzip as soon as the need arrised to create multiple compressed files of a certain size (say, to fill up CD's or dare I say floppies) and haven't looked back. It has a better compression algorythm resulting in smaller file sizes than .zip. In addition, it allows you to vary the relative amount of compression based on the time you want to allocate to your computer crunching numbers as to the best way to compress something. A very important feature allowing you to distinguish between wanting to break a dvd size file up into cd sizes relatively quickly, or highly compressing documents to for email.
Bittorrent Client: Azureus Vuze
I'll be the first one to admit that Vuze is a bit bloated. Now especially with all of the new media channels that originally display, it's really trying to be more than it has to be. That being said, there are some pretty cool features that set Vuze apart. Easy RSS Feed creation - this is something that has always boggled me for Bittorrent use but Vuze makes it easy and quick to set up. Loads of Settings - I haven't been able to find another p2p client with more connection and transfer settings that Vuze