The tool on the cover of Excel Hacks is a trowel. The trowel shown is the type that is generally used in everyday gardening tasks such as removing stones from dirt, planting, and removing weeds.
The cover image is from the Stockbyte Work Tools CD. The cover font is Adobe ITC Garamond. The text font is Linotype Birka; the heading font is Adobe Helvetica Neue Condensed; and the code font is LucasFont’s TheSans Mono Condensed.