Excluding multiplatform apps (Photoshop — can't live without this on ANY computer) and apps that come with OS X (Safari, Mail, Preview, TextEdit, etc... I use a lot of them), my list is probably something like:
- Adium
- Coversutra
- Transmission
- iPhoto — I'll count this as it comes with new Macs but not OS X itself, and is essential, especially if I want to give my iPhone new wallpapers. >.<
I could probably add Transmit to the list, but I don't FTP a lot at home and don't have Transmit at work. 🙁 Or maybe it's because CyberDuck is so slow and crashy.
I also might have added either Quicksilver or Launchbar, but since Leopard came out the new Spotlight has been "good enough" to warrant having one less application running in the background.
Also, Inquisitor is fantastic, though not really an application per se. Same goes for Safari AdBlock (the Leopard-only one) which is torturous to live without.
And without Perian I'd be forced to watch things in VLC, which used to be essential, but is falling behind the times recently.
It's hard to leave Toast off the list too, cause when I need it, nothing else will suffice.
Yeah, it's hard to keep the list to 4 apps. 🙂