Aside from Eve, in her conversation with Satan, adding "neither shall ye touch it", the first lie mentioned in Scripture was told by Satan to Eve, and it is a lie taught perpetually today from many church pulpits (#1).
1. Disobeying God will not result in death
2. Disobeying God will bring greater wisdom than God has already given
There is a half-truth to #2, because the disobedience would bring a knowledge of evil that Eve previously had not known.
Genesis 3:1-5 "Now the serpent was more subtil than any beast of the field which the LORD God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden? And the woman said unto the serpent, We may eat of the fruit of the trees of the garden: But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die. And the serpent said unto the woman, Ye shall not surely die. For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil."