Feeble top-attack javelins, Tow-2Bs, Gills, Bills, Spikes etc.. sit on that hill with whatever on front turret/hull HEAT armor and there is a good chance of being penetrated from the top. At least when thinking campaign games or e-mail opponents you become very aware of these nasty devils after seeing a few burning elite merkava 4s (750-800 points gone to overconfidence
).
Also fo-directed artillery cluster munitions, or a old feeble F-5 with cluster bombs.
Do not sit on hill tops seen and waiting to be killed (unless you have top armor of 70 atleast).
The AI maybe stupid, but it surprises me ever more often.. thanks to the game developers for that!