In the LispLanguage family, but using the sophisticated object system from CocoaFramework / GnuStep. I say "sophisticated" partly because it inherits a nice class library, but also because it's based on message passing like SmalltalkLanguage. I think it makes pretty much all the right compromises to achieve this, but it does lose something from both sides: from the SmalltalkLanguage side, it loses the idea that EVERYTHING is message passing (although all the Cocoa calls are in message-passing style, and you can write all your own functions in message-passing style if you like ... but not macros); and from the LispLanguage side, it loses multiple inheritance.
Even if you're not interested in the object system, it's neat to have a LispLanguage that optionally uses message passing and keyword parameters.
I am currently attempting to install Nu on UbuntuLinux using Nu.0.4.0.tgz. After a while this comes to a grinding halt. I will post the solution when I find it. The answer was that the instructions I was following were out of date. Following different ones I have been able to build the shell for nu. The detailed answer is to follow instructions given for DebianLinux which involve using GnuStep 1.18.0. --JohnFletcherCategoryProgrammingLanguageCategoryLisp