Some of my favourites are:
Pending clearance;
On climb/descent;
IFR taxi (already mentioned);
Maintaining (in radar environment or when changing frequencies).
But the one that really makes me laugh:
"Centre ABC request."
"ABC go ahead."
"ABC request FL350 IF AVAILABLE!"
All that needs to be said is "ABC request FL350". If it's not available you will not get it. Simple.
While I'm at it, who decided that The words "diagonal" or "oblique" belong in an airep? The wind is described as "250 degrees 17 knots". Jepps meteorology section.
C100 driver, it has already been pointed out why "leaving" is the required word and not "left". Again, it's what Bloggs said. Just say what you are required to say and if ATC think it's not appropriate then they can change it.