I play a lot of OP14 for operational WW1 games and NATO Brigade Commander for WW2 and moderns. They are both a bit obscure as they were only really published in the Wargames Developments Journal. Also a huge fan of De Bellis Navalis by Colin Standish, DBA with battleships. Published in WI in Jan 2000.
I used to play Lost Battles a lot but these days I prefer Command and Colours Ancients.
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke