Here's a tipe for survival mode or campaign too: First: buy the boomstick and max it, chose the redneck aim perk when u reach the lv(i think its 15, idk i forgot), when maxed, buy the last armor(or buy it be4 the boomstick, do as ur will) than buy the rechargable critter and pick the pecks improved gadgets and 00 gadgets (to upgrade the rechargable critter) and its all, u'll see, u get a kilin machine with this tipe, instant kill any enemie with 2 shots(expect the FBI agents)
THIS GAME IS THE BEST TD EVER, I BET NO1 CAN BETTER (without copying ofc) the only thing they could upgrade in this game is a reset point and like new spells like summonin soldiers or block in the path.