Correlation taken as Causation has to be the top one:

• Study finds link between depression and video games -> video games cause depression
• Study finds link between homosexuality and suicide -> homosexuality damages the brain

Second would be misjudging proportions:

• Working out burns calories, so going for a 30 minute run (burning 140 kcal above resting rate) will compensate for the chocolate (350 kcal) I just ate. Shit, I deserve an extra one because it was cols outside.
• Vaccines have a 0.1% chance of bad side effects, so I’d rather risk my child having a 5% chance of getting crippled from disease.