A lot of people use text editors such as Textpad and EditPlus. My favourite is Textpad; it can handle large files and also has a very good interface.
Many times we need to search for muliple words in a line. For e.g. in a log file, search for all lines having words 'abc' and 'xyz' on a single line. Using the regular expression search facility available in these editors, this task becomes a piece of cake.
RegEx for the above task: abc.*xyz
We can keep on adding more words - abc.*xyz.*123
A simple feature, but very powerful while analysing logs etc.