None. Every one of them fills a purpose, even if the purpose is just my desire to own and handle them.
Why no regrets? Because I never buy without trying, so I always have at least some idea of what to expect. Plus I never buy a user knife under 30 or over 150. Keeps "China Stainless" brand away from my pockets, and there are no unrealistic expectations. If I buy a, say, a cheapo push dagger, it's not for using many times. I just tape it somewhere and hope to never use it.
In the 50-100 price range there are rarely any surprises or disappointments, if you don't go for the gimmicks and fads.