Assuming that you type a lot, you might like these useful keyboard shortcuts for quickly deleting text. That is, if you make mistakes.
The "Delete" key obviously removes the single character behind the cursor. We hopefully discovered this in Typing 101.
Option + Delete: deletes a whole word prior to the cursor.
Command + Delete: deletes the entire previous line.
Function + Delete: Deletes the character in front of your cursor. This can be stacked with the Option key to perform a forward delete of an entire word.
And for extra credit, the Arrow keys will also behave according to those shortcuts (eg. Command + Left Arrow moves the cursor to the beginning of the line).
Anyway, the power users among us might find these keyboard shortcuts a bit pedantic, but I was shocked when I did them in the presence of a buddy at the Apple Store, and he thought I was working magic.