I thought about this on & off over the last couple of days and came up with more candidates than you can shake a shitty stick at. Some of these are somewhat political or controversial, but I don't think any are reliable flame-war magnets. I expect some'll ring your cherries more than others, but since I can't tell which, I'll post 'em all and let you decide.

1. The answer to the Sleeping Beauty puzzle is obviously 1/2.

2. Rational behaviour, being rational, entails Pareto optimal results.

3. Food availability sets a hard limit on the number of kids people can have, so when people have more food they have more kids.

4. Truth is an absolute defence against a libel accusation.

5. If a statistical effect is so small that a sample of several thousand is insufficient to reliably observe it, the effect's too small to matter.

6. Controlling for an auxiliary variable, or matching on that variable, never worsens the bias of an estimate of a causal effect.

7. Human nature being as brutish as it is, most people are quite willing to be violent, and their attempts at violence are usually competent.

8. In the increasingly fast-paced and tightly connected United States, residential mobility is higher than ever.

9. The immediate cause of death from cancer is most often organ failure, due to infiltration or obstruction by spreading tumours.

10. Aumann's agreement theorem means rationalists may never agree to disagree.

11. Friction, being a form of dissipation, plays no role in explaining how wings generate lift.

12. Seasons occur because Earth's distance from the Sun changes during Earth's annual orbit.

13. Beneficial mutations always evolve to fixation.

14. Multiple discovery is rare & anomalous.

15. The words "male" & "female" are cognates.

16. Given the rise of online piracy, the ridiculous cost of tickets, and the ever-growing convenience of other forms of entertainment, cinema box office receipts must be going down & down.

17. Looking at voting in an election from the perspective of timeless decision theory, my voting decision is probably correlated and indeed logically linked with that of thousands of people relatively likely to agree with my politics. This could raise the chance of my influencing an election above negligibility, and I should vote accordingly.

18. The countries with the highest female life expectancies are approaching a physiologically fixed hard limit of 65 — sorry, 70 — sorry, 80 — sorry, 85 years.

19. The answer to the Sleeping Beauty puzzle is obviously 1/3.

Language in general might be a rich source of these, between false etymologies, false cognates, false friends, and eggcorns.