Interesting question :) I'm not sure if using one tool or programming language will alter a person to become more youthful (Delphi?), anal-retentive (SML?) or bitter (COBOL?). But I'm convinced the opposite is the case -- that different personality types are attracted to different programming languages, tools, and methods.
For the sake of argument (and for fun, really), I'll take the Enneagram as a starting point, and try to make an educated guess at what languages each personality type might prefer.
Disclaimer: I am no psychologist, and I don't know hundreds of different languages. In essence: all of the below may be complete bunk.
Well anyway, here goes:
1. The Reformer
The One's attention goes to appreciating the excellence and elegance in anything such as a shape, musical score, a piece of art or a speech; to noticing and correcting errors; to identifying and adhering to standards of perfection in thought, feeling and behavior.
Technology/Language preference: Anything 'clean', standards-compliant and highly optimized. A clear preference for assembler and low-level C code.
2. The Helper
The Two's attention goes to interpersonal relationships and paying attention to important people, to giving to others, and to gaining approval.
Ideals: Humility, freedom
Technology/Language preference: Probably wouldn't be a coder in the first place, but would probably write some of the best commented/documented code you've ever seen. Proponent of and contributor to open source projects.
3. The Achiever
The Three's attention goes to setting goals and hitting their targets, to success and creating the "right" image in the eyes of others, and to doing rather than being.
Ideals: Success, hope
Technology/Language preference: Prefers efficient, fast, low-learning-curve tools - anything that helps reach his goal quickly without sacrificing code quality. Uses C#, Python, Ruby on Rails, etc. Holds code to a very high standard, hates bloat and other people's buggy code.
4. The Individualist
The attention of Fours goes to what is missing and desired, to loss, to emotions, to drama, and to longing for the ideal and distant ? thus, the sense that the heart is broken or damaged in some way.
Technology/Language preference: Esoteric or specialized languages like Ada, Smalltalk, Prolog, or even Lisp. Would fake their own death to avoid working with mainstream tools or languages like C++ or ASP.NET. Probably has the craziest casemod in the company, and might not be running any O/S you've ever heard of.
5. The Investigator
The Five's attention goes to gathering knowledge and wisdom, to thinking and observing, to protecting inner resources and to warding off intrusions from the outside.
Technology/Language preference: Only uses 'academically correct' tools and languages. Insists on best practices in testing, development, coding style, security, etc., completely without regard for practicality or economic viability. Uses Python, Perl, SML, C, etc. depending on situation.
6. The Loyalist
The attention of Sixes goes to questioning and doubting, to scanning their environment for signs of threat and danger, to searching for proof to confirm an inner sense of threat, and to creating worst-case scenarios.
Ideals: Faith, scepticism
Technology/Language preference: Will do his job regardless, but prefers strongly typed languages with garbage collection, e.g. Java. Paranoid about thread safety, bad pointers and stack overflows.
7. The Enthusiast
The Seven's attention goes to options and possibilities, to seeking pleasure, to avoiding pain and discomfort, and their minds typically shift quickly from idea to idea. Sevens like to keep the mood upbeat, and so engage in elaborate future planning, playful interactions, and enjoyable activities. They typically have many interests and active imaginations.
Ideals: Pleasure, opportunity, optimism
8. The Challenger
The Eight's attention goes to issues of power and control, to making things happen, to protecting the weak, and to fighting injustice. With an intense, authoritative, and sometimes explosive energy, they are usually ready to face any challenge.
Ideals: Power, truth, vengeance
Technology/Language preference: Prefers telling other coders what to do, rather than doing it himself. Wants practical yet highly flexible tools that never get in the way and can be stretched and bent to do exactly what the coder wants. Likes languages like C, Lisp and perhaps Python.
9. The Peacemaker
The Nine's attention goes to connecting with others, maintaining harmony, peace, and comfort, and avoiding conflict. They typically enjoy a feeling of ease, harmony, and peace.
Ideals: Conflict avoidance, love
Technology/Language preference: Will adapt to whatever language he is asked to use or maintain. Likes weak typing and interpreted languages with just-in-time evaluation. Probably has a habit of silencing errors with empty catch(Exception e) blocks.