SQL Tool

SQLTools is a light weight and robust frontend for ORACLE database. It offers a powerful text editor, a sql console, object browser and a few useful tools.

It has small footprint and it is fast as Oracle SQL*Plus. SQLTools does not need an installation so you can copy it on usb stick.
SQLTools is not comprehensive as TOAD or PLSQL Developer and never will provide so much functionality but some people like its clean and fast UI.