1. MySQL GUI Tools (http://dev.mysql.com/downloads/gui-tools/5.0.html)
The MySQL GUI Tools Bundle includes:
* MySQL Administrator 1.2
* MySQL Query Browser 1.2
* MySQL Migration Toolkit 1.1
2. HeidiSQL (http://www.heidisql.com/)
Both are pretty similar but sometimes the little difference is the crux of the matter.HeidiSQL is an easy-to-use interface and a "working-horse" for web-developers using the popular MySQL-Database. It allows you to manage and browse your databases and tables from an intuitive Windows® interface.
Both tools require an installation by default, but have no dependencies that would label them as not portable. Still I could not guarantee, that they don't write somehting to the registry or the user folder.
(Just recognized that DBdesigner4 was rejected because of that point - pity, because it is still really useful if used portable. By the way: The successor of DBD4 - MySQL Workbench (http://dev.mysql.com/downloads/workbench/5.0.html) has been released in a new version last month and also comes with a download option "no install" - still a beta and no reverse engineering ooption available :-/ )
You might also use some extraction tools like Universal Extractor to circumvent the installation. I use them in combination with the Uniform Server, since the database handling is much more convenient this way than with phpMyAdmin.
Well, just thought here is a lack of such tools