The CCENT and CCNA.
Introduced in June 2007, the CCENT is a stepping stone to the CCNA. Prior to 2007 the CCNA exam was multiple choice. After 2007 the exam was administered as mostly a "Lab Simulator", meaning, the test question would say, "There is a network issue, log in and fix it. Click next when you are done".
The CCNA exam is a timed test taken at a secure facility, and is not allowed to be administered by any educational institute where CCNA materials are taught. The CCNA is only obtained thru one of these secure testing centers by appointment only. The exam carries an 85% failure rate accross the board.
It is an extremely tough test.