Complimentary and Complementary
Aren't you annoyed by the flurry of all those complimentary everything-and-nothings? What's wrong with just saying it's "free"? Of course, as usual with smart buzz words, for the thick and self-conceit, there's always the risk of mis-use -and this is the raison d'ĂȘtre of this blog.
For this word, the proximity with complementary is just to tempting not to Google for a giggle, for instance in this PDF: on page 4, the first title is interesting :-)