I'm currently learning Elixir at a new job, and I really, really dislike the (what I think of as) the ruby-style where `return` statements and function call parentheses are optional.
To be consistent, we could choose to always add "return" to the last line of every function -- because that's what it's doing. But this is a completely redundant bit of typing once you know what the language is doing. Having that "return" on the last line of every single function is not helpful in the least. Instead we can define "return" to be a statement that you only use when you are returning early from a function.
Since he pointed that out, languages that force me to type "return" at the bottom of functions bug me :-) As for parentheses, I'm mostly in agreement. Omitting parentheses is mostly useful when you are writing a DSL where you want to obfuscate that what you are doing is actually a function call. In Ruby land, Rails uses this effectively. However, it's a double edged sword because I have seen junior developers who do not understand that this is normal Ruby and a function call. They just think it is "Rails Magic". I'm of mixed feelings on the matter. I use it occasionally when I feel that it helps express the intent of my DSL rather than the plumbing, but I always feel a bit uneasy when I do it.
Same thing for implicit return statements, when they're implicit it just takes getting used to the fact that the last statement in the block returns -- I've never really had trouble reading code because of the lack of function call parentheses or explicit return statements but I guess in a language where it's optional it can be a bit more unexpected versus a language like Haskell where this style is encouraged more strictly.