Patlabor is another good example of at least a semi-realistic look at giant robots. The labors are smaller sized and are mostly used for construction, fire/rescue and police duties (military labors were introduced later). Excepting obvious anime in-jokes like the Ingram, the labors are very functional in design.
Another interesting take on this subject is an essay that Shirow wrote concerning legged tanks. His proposed design for a low to the ground, hexapodal tank would work pretty well, given that you can get all the engineering worked out.
As for Heavy Gear, I do like their designs (glad I'm not the only one who spotted the VOTOMs influence; a lot of HG fans are in denial about this), but a lot of the reason for why they work so well in the setting is due to Terra Nova itself. IIRC, the area where all the fighting occurs is a very difficult place to use aircraft in and limits the use of long range weaponry because of high winds and heavy magnetism (which conversely allows them to use those big hovering battleships).