Cal Murphy (by Jack Patterson) uses Cross in the title - "Cross Hairs", "Cross the Line", "Triple Cross". (http://www.amazon.co.uk/Jack-Patterson/e/B0098F2E48/ref=ntt_...) (This last one feels odd - the author name is close to James Paterson, and the series titling uses a word ('cross') that happens to be the name of the James Paterson protagonist.
You'd be surprised! Some of these are weaker than others.
Stephanie Plum (By Janet Evanovich) start "One for the money", "two for the dough", "three to get deadly", "four to score", etc etc. (https://duckduckgo.com/c/Stephanie_Plum_books)(This is a terrible website)(http://stephanieplum.com/)
Hannah Swenson, 'murder she baked', has food in each title (and a recipe in each book) (admittedly, the titles aren't in any order) (http://www.amazon.co.uk/s/ref=nb_sb_ss_i_0_14?url=search-ali...)
(http://www.amazon.co.uk/Janet-Evanovich/e/B000APXTY4/ref=sr_...)
Women's Murder club. Each title starts with an incremented digit. "1St to die", "2nd chance", "3rd degree", etc. (http://www.jamespatterson.com/books_wmc.php#.Uigpk9KRC0I)
Alex Cross, (By James Patterson) starting to get Children's nursery rhymes in the titles. (http://www.jamespatterson.com/books_alex_cross.php#.UigpyNKR...)
Cal Murphy (by Jack Patterson) uses Cross in the title - "Cross Hairs", "Cross the Line", "Triple Cross". (http://www.amazon.co.uk/Jack-Patterson/e/B0098F2E48/ref=ntt_...) (This last one feels odd - the author name is close to James Paterson, and the series titling uses a word ('cross') that happens to be the name of the James Paterson protagonist.