Panzer 2. Early WW2, armed with a 20mm autocannon.
Not really for engaging other tanks, but pretty bad news for lighter targets. They were used for scouting, infantry support, raiding... whatever didn't involve going after enemy medium or heavy armour if they could avoid it. Actually quite small, which the second to last pic shows best.
The fact French tanks (for example) were substantially more dangerous didn't matter when the swarming German light tanks overran them, kept going, stole all their fuel and blew up their ammo stockpiles; allied armour in trying to pursue them ran smack into the sights of dive bombers and the towed german AT field guns the clever Germans left in their wake.
Classic example of using what you have to maximum effect, to overcome an (on paper) superior enemy.