Gaming devices, gaming systems, methods of conducting wagering games, and computer programs for executing wagering games are disclosed. A gaming system for conducting a wagering game includes an input device, a display device, a processor, and a memory device. The memory device stores instructions which cause the processor to operate with the display device to: randomly determine an outcome of the wagering game; display symbols indicative of the wagering-game outcome; determine if the displayed symbols include to an expected-value (EV) enhancement symbol combination or an EV-elimination symbol combination, the EV-enhancement and EV-elimination symbol combinations both including a common symbol arranged in a common manner; activate, responsive to the displayed symbols including the EV-enhancement symbol combination, an EV-increasing opportunity that modifies a wagering-game parameter thereby increasing the EV of the wagering game; and deactivate, responsive to the displayed symbol-combination corresponding to the EV-elimination symbol combination, one or more EV-increasing opportunities.