1. You can only buy whole bitcoins.
One of the most common misconceptions, but also an excuse why someone has never bought Bitcoin - because if they can't have 1 BTC, they don't want to have 0.01 or some similar amount.
2. It's a ponzi scheme/ tulip bubble/ some other kind of scam or shenanigans.
Bitcoin is unfortunately largely a victim of all those online scams that have happened in the past, so for some people everything on the internet is a scam in one way or another. Those who think this way have never even bothered to see the difference between Bitcoin and some Ponzi/MLM scheme.
3. I would love to buy some Bitcoin, but (whatever the current price is) is just too expensive for magic internet money. This one I think is due to people feeling like they missed out at being an early adopter.
I think this has something to do with what was described in the first case, because there is not much logic if someone says that 1 BTC is expensive for him, and when you explain to him that he can buy an amount worth $20 or even less, then it all boils down to the fact that such small amounts do not have sense. Being jealous of those who knew about Bitcoin in the first years of its existence is completely stupid, because Bitcoin was not a closely guarded secret, anyone could be among the early adopters.
What are your favorites?
Bitcoin is destroying planet Earth and we will all be left in the dark because of POW + it is only used by criminals and drug dealers, and of course the ever-present terrorists.