Well, just want to point out, that it is possible to mortar in the tunnels on oasis, or in the basement on the beach, (all on axis side) and also mortar into the windows on the Warbell (all on customs server). (My in-game nick is ==Troy== :) )
The idea of that is setting your mortar on a slope surface, this will change the regions of possible angles of firing (default one's are 40-90 degrees) the slopes can change it up to -10 to 40 degrees, which allows you to do a straight shot, like a panzer.
Advantages:
+Works as panzer
+Faster than Panzer.
+More ammo than panzer
+Much more powerfull than panzer
+Warmup time is smaller
Disadvantages:
-Long time to set mortar, so can be used only for defence.
-Fixed region of angles and fixed position of shooter
-Harder aiming
Tip: When you are aiming with mortar, Keep looking at the place where you are shooting, when you see somebody, press fire, and THEN change the angle to the proper one, while the mortar warming up you will be able to set the angle, which will save you a second or so.
Well, that' actually it. I like messing up with mortar and it's a good defencive weapon on oasis, if the server is crowded, but mortar is nothing without support or ammo, which you will run out fast :).
It is also possible to set mortar even on stairs, if you are lucky (I can do it 1 out of 20 tries). So actually there are a lot more places to use it in a unusual way :).
But well, next time I will ask you before posting such tricks :)