depends on what exactly you want to reset to default. you might need to restore with time machine, reinstall mac OS X, uninstall the program, or there may be a restore settings to pre-"program name here" such as tinkertool. tinkertool doesn't really change looks of leopard, but it tweaks various aspects of it. anyway it's got a reset option that resets your settings to what they were before you installed it.
there are various dock tweaking applications. what do you have against candybar by the way? i use it and its great.
anyway, dock apps:
dockcolor (only changes dock by color slider)
superdocker (various system tweaks and ability to apply custom docks)
dockdr (add recent items stack and apply custom docks. also comes with a few built in ones like dark glass. that's my favorite. however, dockdr stopped working for me so i took the dark glass file and saved it in superdocker format and uninstalled dockdr.)
dockdodger (remove running apps from the dock that you don't need there by dragging the app into the dockdodger window. to put them back just drag them there again. i use this for a better finder launcher.)
magnifique 2.1 is a leopard theme manager that lets you download and install leopard themes, but it's somewhat slow, and i'm a bit suspicious that it's somewhat of a trojan, although my antivirus says its clean. i'm only suspicious because i haven't heard much of others using it really, and EVERYONE wants new leopard themes.
service scrubber lets you tweak the services menu under the application menu of running applications. you can change those shortcut keys too. i never used services before but i do now. some are really useful.
hm thats about it for what i know of. i'd suggest candybar and secrets even though you said you don't want them. both really useful.