Not an entry in the poll, but man I hate the keyboards that show up in ex-French colonies such as Morocco and various locales in Southeast Asia. The keys are 'mostly' in place except for an annoyingly few exceptions -- I'd rather it be totally mangled rather than just 'here and there'.
in reply to The most useless key on my keyboard is:
Update: well, I initially misread the poll, so perhaps I should add that my answer is 'those annoying keys on french colonial keyboards' ... at first I thought the poll was about keyboards rather than keys. :)