This is something I've typed way too many times:
Py> class C(): File "<stdin>", line 1 class C(): ^ SyntaxError: invalid syntax
It's the asymmetry with functions that gets to me - defining a function with no arguments still requires parentheses in the definition statement, but defining a class with no bases requires the parentheses to be omitted.
Seconded. It's always irked me enough that it's the only ``apology'' for Python syntax you'll see in the Nutshell -- top of p. 71, "The syntax of the class statement has a small, tricky difference from that of the def statement" etc.
+1 For me, this would come-up when experimenting with mixins. Adding and removing a mixin usually entailed a corresponding change to the parentheses. Raymond