a direct energy weapon perhaps ? one that fires a continous stream for say 3-4 seconds with just a little bit of burn damage (to help you get that kill :P). shouldn't be able to penetrate more than 1 tank, should take as much as thunder to reload after emptying the charge completely. and maybe change the colour of the lazer with each modification

how about a hull that floats ? we've all seen concept art of futuristic tanks that have no treads, like one that has anti-gravity generators underneath. said hull wouldn't be affected by mines but in order to balance it out it can be afected more by the kick back (or recoil) of weapons it fires or when it's been hit--since it has no treads--the impact should end up even driving it off course when shot by ricochet or smoky. what do you guys think ? thank you for your time :)