De Bellis Antiquitatus is a wonderfully fun and very fast pre-gunpowder wargame. It is also surprisingly cheap: rules under $10, $15-30 per army. The only catch (at least for a horribly busy college student) is the time needed to paint figures.
Legos solve the figure problem as well as giving a benefit to make up for the lack of detail: interchangable armies. For example, the Numidian army in blue was first a Gallic army--the only change (aside from the elephant) is rebasing.
Building on this scale forced some sacrifices in realism (so what if the horses look a bit like dachshunds), but I've aimed more for easy recognizability--after all, old computer games like Centurion hardly offered more "pixels" than careful Lego work. Lego economy is also an issue.
As for game details, the units are based roughly according to 25mm rules, with one lego stud = 10 mm, about 80% of real DBA 25mm. Most troops have an appropriate "figure" count; the exception is line troops which are all straight lines. These are differentiated with appropriate weapons (spears and blades below). The armies are Camillan Roman (Red) and Numidian (Blue). A leftover Gallic command chariot is included--note the horned helm.
