Documentation: MS Word. Knowing how to use Word is not an end in itself but a means to various ends; what really matters is to put Word to effective use for the unique, specific purposes of your project.
Presentation: MS Powerpoint. Similar rules as above.
Data Analysis: MS Excel, SQL querying.
Modeling, Flowcharts: MS Visio, eDraw.
Wireframing, Mockups: Pencil, Balsamiq, MS Visio.