Death Tank

Since they've update the game, this is so quick to get. Go to create game and go down to mods. Go into every option and un-check everything. Once thats done, go to the heavy weapons and go down to the Rolling Nuke, and max out/minimize the options to your likings. (min cost and weapon loading/ max shots, damage, and range). Also make sure you put a check by start and theme. Then back out and set the option so that you get a Theme round every time. Put 7 A.I. opponents in and start. Just keep clicking the 'A' button and you will get kills instantly. Do this for however long you want to get kills.

Lucas1987's guide is awesome. But you don't get alot of kills because the AI also gets kills every round. I have a solution were you get every kill every round. Actually, the AI wont even shoot....period. Here are the mod settings you need.

Starting Cash - 1000
Tank Health - 1
All weapons and equipment off except - rolling mine and target comp
Theme Rounds - Off

Now set Rolling mine to these settings
Charge rate - lowest
Cost - 500
Damage - Anything above 1

Set Shell to these settings
Charge rate - highest
Damage - 0

And make Target Comp 5 dollars each.
Set Bombardment to 30 Sec. in case you kill yourself...you won't have to wait to long.

Now start the game and buy Rolling Mine and 20 Target Comp. The computer will just sit there with shell, waiting for it to charge. You can then kill each one with your Target Comp and Rolling Mine before they even get a chance to shoot. Doesn't matter if they shoot anyway though since shell is set at 0 damage :)
Every 100 rounds gives you 700 kills. That is...as long as you don't kill yourself and set AI opponents to 7. Hope this helps!