my opinions are..
1. The placebo effect. The subconscious mind will do whatever it takes to satisfy the person. Possibly certain self curing abilities
are natural to the human body if the person chooses to activate such abilities.
2. The horizon problem. There is a severe problem in our technology in that it is the same telescope technology for the last three hundred
years. It is possible human error compounded with limited technology causes this "box in" effect.
3. Ultra-energetic cosmic rays. Again the technology limit.
4. Belfast homeopathy results. Modern science is heavily biased against old world technology. Many things do work, but are heavily under uzitilized in favor for modern medicine which in my opinion is more hocus pocus than traditional medicine. Trial and error by a peasant by sheer effort and time will work much better due to the elimination of the errors over years than by just sample month trials alone.
5. Dark matter. Likely black holes that cannot be spotted.
6. Viking's methane. Major problem no skeleton has been found on mars yet.
7. Tetraneutrons. Probably a hoax experiment.
8. The Pioneer anomaly. human error at the rounding off at decimal place.
9. Dark energy. Unproven observation.
10. The Kuiper cliff. Nothing in space past pluto.. might be there is a limitation to the gravitational field of the sun.
11. The Wow signal. Random space noise.
12. Not-so-constant constants. Too many assumption about light and how reality works.
13. Cold fusion. I have yet to see a lab experiment that really works with this. As well as a working better definition of cold fusion.