I do Ancients in 15mm since 1977. I've been using DBM for the last few years but now I'm the Portuguese translator for the future Field of Glory rules,to be published by Osprey Books in about 6 months time.
Free plug here
http://www.ospreypublishing.com/osp_img/specialfeatures/US_Spring08_frontlist.pdf pages 19-20
In WW2 I use God's Own Scale, that is, 6mm

I use a derivative of Spearhead rules. Before that I used Firefly.
That's one of my Matildas in France '40 scheme. The ruler behind is in mm
I also have lots of Ancients in 6mm, and large US and USSR forces for WW3 pre-Perestroika, but the rules I had, Challenger, were too fussy and you couldn't finish a game. Perhaps I'll find the gut to try with Modern Spearhead...