thebes: The flak 88 cannot shoot at tanks? Really? One of the best anti-tank weapons of the war! PG2 by the way.
No, you're right, the anti-air version can't, but if you look under anti-tank units they have the 88 (although, I think it's called 8.8 cm instead of 88mm) same gun, but angled to the ground. And yeah, the Germans really learned something when they shot their 88's at tanks. Because of the high-velocity shells, the tank's armor was shredded.
Note: I always try to get an anti-armor 88 because of it's range (2hexes). It can't do much in the beginning of the game. I call it 'soft artillery' because although it rarely does much damage, it does lower the enemy's defense the same way an arty strike would. Occasionally, it can hit a retreating unit for a good smack and earn some nice EXP for the effort. LATER, when the same unit has earned a lot of XP (and really hopefully a hero), I upgrade him into a nice PanzTiger or Hetzer or something and use him against some serious armor. Those great units come later in the game and there isn't enough time to get them XP, much less a hero, but I find this strategy works really well.