[Tloewald]

* case sensitive symbols in C and its derivatives -- thank goodness I can declare int Int.

* C declarations (experts can get into flamewars discussing good ways of reading C declarations)

* C (and worse C++) keyword overloading

* C strings

* Most of C++ (i.e. most of C++ - C)

* Most Java libraries

* Objective C's declarations (which at least have gotten markedly better recently)

* Perl's variable prefixes and subroutine declarations (even if you don't mind Perl's other quirks)

* semantic whitespace in languages with semantic whitespace

* PHP -- which I find useful and perfectly capable of supporting large projects -- is hilariously awful.