My favorite is Common Lisp. The ones I use regularly for work are Common Lisp and Perl (mostly because of CPAN). I like Common Lisp because of interactive development, the large size of the language, the fact that it's easy to make abstractions, the fact that it's easy to write very readable code, it's multiparadigmatic nature, and many other reasons.
Common Lisp will give you another take on OOP. So will (for example) Smalltalk (which I also use occasionally - for example, Dolphin Smalltalk gives one a good way to do the types of things (and others as well, of course) that Visual Basic is intended to do). Any specific Smalltalk you may choose is also likely to be a "large language".
