Thats easy, wheatbacks. Cant stand the darn things because there is just so many of them. Add to the fact the coin has been around for 103 years. Sure its had reverse changes but I dont count that its too long. And on the ancients side... Roman Emperor Gordian III. He's a wheatback of ancients. Though he is silver and had many many reverse to choose from, he's still way too common. Wish he made some more of his wife then just himself.
Roosevelt dimes. They swapped the winged liberty for that! Not saying anything bad about the man. Just my opinion.
The new shield pennies are pretty jank. I also dislike state quarters, journey nickels, presidential dollars, and boyhood cents. All of that just seems gimicky. As far as historical issues go, I'd have to say Coronet head cents (1816-1835). Liberty looks like a frumpy old woman on those coins.
I like Ike, I like Ben but I don't like the current Prexibux series nor do I like SBA dollar (obverse only).