Mihai Parparita is asking on Mastodon:

What are good examples of early Mac OS X software (10.0-10.4 era, pre-Intel switch)?

Then providing the initial list.

OmniWeb, OmniGraffle, OmniOutliner and other Omni Group software

Transmit 2, Unison, Candy Bar, Pixadex, and other Panic software

Audio Hijack and other Rogue Amoeba software

NetNewsWire and MarsEdit

Watson

Acorn

TextMate

Quicksilver

VoodooPad

BBEdit

SubEthaEdit

GraphicConverter

iCab

Camino

Fetch

Default Folder X

MenuMeters

DEVONthink

CodeWarrior

Resorcerer

FruitMenu, WindowShadeX and other Unsanity haxies

LiteSwitch X

DragThing and PCalc

TinkerTool

LaunchBar

Path Finder

Konfabulator

Good memories, although most if these are still alive and well.