Yep, Rose Mary Woods.
Chief Minority Counsel Fred Thompson put the question to Butterfield directly in televised hearings: "Mr. Butterfield, are you aware of the installation of any listening devices in the Oval Office of the president?" The shocking revelation radically transformed the Watergate investigation. The tapes were soon subpoenaed by Cox and then by the Senate, since they might prove whether Nixon or Dean was telling the truth about key meetings. Nixon refused, citing the principle of executive privilege, and ordered Cox, via Attorney General Richardson, to drop his subpoena.Source
...While Nixon continued to refuse to turn over actual tapes, he did agree to release edited transcripts of a large number of them; Nixon cited the fact that any sensitive national security information could be edited out of the tapes; it was also speculated that the tapes may have contained foul language and racial slurs, which would have worsened Nixon's image.
The tapes largely confirmed Dean's account and caused further embarrassment when a crucial, 18½ minute portion of one tape, which had never been out of White House custody, was found to have been erased. The White House blamed this on Nixon's secretary, Rose Mary Woods, who said she had accidentally erased the tape by pushing the wrong foot pedal on her tape player while answering the phone. However, as photos splashed all over the press showed, it was unlikely for Woods to answer the phone and keep her foot on the pedal. Later forensic analysis determined that the gap had been erased in several segments — at least five, and perhaps as many as nine refuting the "accidental erasure" explanation.
Some of PM's defense talks before last year's war went unrecorded
Some of Prime Minister Ehud Olmert's conversations with senior defense officials shortly before last year's war in Lebanon were not recorded due to a "malfunction," and certain others were intentionally unrecorded, Olmert's bureau chief Yoram Turbowicz told the Winograd Committee.
...Turbowicz said that shortly after the incident that sparked the war - Hezbollah's abduction of two Israeli soldiers - Olmert spoke by phone with then defense minister Amir Peretz and then Israel Defense Forces chief of staff Dan Halutz. When the committee noted that it had no transcripts of these calls, Turbowicz replied: "Not everything is recorded because there are malfunctions, as with everything in this country. So important things are suddenly not recorded."
In addition, he said, some of Olmert's conversations were intentionally not recorded, to facilitate free discussion.
We've come such a long way since 1974.
Not really. Just kidding.