Really?

I liked Equal Rites more than anything with much of Rincewind.

Off the top of my head Lords & Ladies is my favorite, but reading Wyrd Sisters, and Witches Abroad sets it up (as does Equal Rites to lesser extent), otherwise I thought that

Mort

Guards! Guards!

Men at Arms

Hogfather

The Last Hero

Night Watch

The Wee Free Men

A Hat Full of Sky

Wintersmith,

and

I Shall Wear Midnight

were all standouts in the series.