What are the default QuickLook plugins in /System/Library/QuickLook/ under OS X 10.8?
I try to do what I can, unfortunately I did not exactly 10.8, I would like to point out that the following list is for

System Version: OS X 10.9.3 (13D65)



Audio.qlgenerator
Bookmark.qlgenerat
Clippings.qlgenera
Contact.qlgenerato
EPS.qlgenerator
Font.qlgenerator
Icon.qlgenerator
Image.qlgenerator
LocPDF.qlgenerator
Mail.qlgenerator
Movie.qlgenerator
Notes.qlgenerator
Office.qlgenerator
PDF.qlgenerator
Package.qlgenerato
SceneKit.qlgenerat
Security.qlgenerat
StandardBundles.ql
Text.qlgenerator
Web.qlgenerator
iCal.qlgenerator
iChat.qlgenerator


Then in addition to /System/Library/QuickLook/
there is also /Library/QuickLook/ 
where I found:

iBooksAuthor.qlgenerator
iWork.qlgenerator