People like me, who grew up using the keyboard and control key instead of the mouse will really appreciate these tips. Of course all of these shortcuts are available in the menus as well.

Control + M = brings up the Memorize Transaction option
Control + Delete = Delete the selected line in a transaction
Control + Ins = Insert a blank detail line in a transaction
Control + N = Create a new transaction or list item
Control + D = Delete the current transaction or list item. Please note that you cannot reverse this once done, usually
Control + E = Edit an item in an item list, or in a register

In a date fields:
+ (plus key) Advance to the next day
– (minus key) Previous day
T Today
W First day of the Week
K Last day of the weeK
M First day of the Month
H Last day of the montH
Y First day of the Year
R Last day of the yearR