Currently at level 51, revolution 3 with about 30,000 kills. If you play the third planet and start from wave 1, you can earn about 3000 coins, 4-5k xp (depending on buffs/bros and how far you get) and 500-700 kills in about 5 minutes. In order to actually get those results you need to use the Blood Geyser spread weapon. It will allow you to take out mass amounts of zombies very quickly in the later waves. Any other weapon besides Heavies won't get you the same results.
Edit: I should also say to keep using Blood Geyser until it's fully upgraded. The first upgrade seemed like it took a long time to get but the other ones came quickly after that. When fully upgraded it will shoot faster, do more damage and critical hit often.
Last edited by VVh1pCr3am; 07-12-2012 at 05:50 AM.