1 - If you create a map with 'default' time set and hold R1, you'll go
through an entire day in about 1 minute...looks pretty cool, and
handy for skipping to a later time of day (for event debugging).

2 - In the map editor, if you go into the 'altitude mode', or 'V-mode'
and hit the 'square' button, this will produce a red area that
represents your water level. Seeing this in relation to your land area
is very useful...but check this out: If you wait for a few seconds, you'll
see that the red color fades, and then becomes opaque again. If you
switch back to terrain mode you can see the water line in relation to
your terrain map, as well. If you time it just right (when the red color
fades), You'll be able to see the relationship more clearly, because the
waterline map will be more transparent.

3 - Holding the 'triangle' button will make your character run, but holding
R2 while you do that makes you run even faster. (Thanks, 'Wavelength'
from the GameFaqs RPGM3 board for that one!).

A lot of people may have been aware of these, but I thought I'd share
them anyway...just in case!

Pretty handy.
What is your game about, might I ask?

From what I tested, holding the R2 button will only make you move faster if you are in gametesting mode. In regular game mode, it only allows for tight turning.