Pronounced "Accidents Grotesque".
History
Akzidenz-Grotesk was released by the Berthold Type Foundry originally under the name "Accidenz-Grotesk" in 1896. Hermann Berthold started his type foundry in Berlin in 1858. The Berthold foundry is famous for creating several new typesetting machines and typefaces, such as Akzidenz-Grotesk (AG). AG was the first san-serif font to be used world wide. As I stated in my Franklin Gothic post, 'Grotesk' or 'Grotesque' was the name used in Europe for what we now call 'san-serif'.
Similarities
AG is commonly mistaken for Helvetica, but AG post-dates Helvetica by 40 years. AG has a more round letterform in its capitals (such as 'C', 'G', 'O', etc.) the its san-serf counterparts. The capital 'Q' has a short ear (leg) offshoot from the bottom-right of the letterform that does not cross into the loop, as it does in Helvetica. AG also has a slab or square dot on its lowercase 'i' and a higher second-story on the lowercase 'a'. Other characters have a more elegant or European-like form, such as the numbers '2' and '7'.
Current Uses
A Chicago company, Berthold Types, ltd. is now the owner of the AG and other original Berthold copyrights. Berthold Types recently (re)released an OpenType version of the AG, named 
The most popular modern use of AG is in the American Red Cross logo.
Visual Study
Sources
http://www.fonts.com/font/berthold/akzidenz-grotesk
http://en.wikipedia.org/wiki/Berthold_Type_Foundry
http://en.wikipedia.org/wiki/Akzidenz-Grotesk
http://new.myfonts.com/fonts/berthold/akzidenz-grotesk-bq/
http://www.bertholdtypes.com/font/akzidenz-grotesk/proplus/
Images used with permission:
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg96wCNz39t3sDJaWPHrRuSxBlAa5-JyViH-S79IQS8Ve9iREtHJa7c5or4fdtJrj6A5tXXkyJK6SOnpBBt3giXrzYvUYMhnzgv2d3DYB0IlkZ-t7AQW6OtOYHBVm0BrQjzYiI5L5fAO3I/s1600/1873363809_8786cf6859.jpg
http://panhandleares.org/wp-content/uploads/2011/02/American_Red_Cross_Logo.jpg
http://upload.wikimedia.org/wikipedia/commons/d/d2/AGcomparison08.svg
