Stop and Go! ($0.99 iOS and Android) by Shortstack is a fun cause and effect-like app about different types of vehicles driving down the street and stopping at a stoplight. There is a school bus, car, truck, ice cream truck, tow truck, tractor, taxi, bulldozer, cement truck, police car, garbage truck, and a motorcycle.
Just from the name of the app you can probably already guess the core vocabulary you will be targeting. Stop and Go of course! I have used this app with new AAC users as “Stop” and “Go” and pretty powerful words to be able to direct the activities of your communication partner as well as to be more of and independent communicator. You can also target “Look”, and “On”, and “Off”. Each vehicle as a “hidden” character or animation. For example when the school bus drives up you do not see any passengers and once you tap the bus the children pop up. This is a good opportunity to work on commenting using “Look!”. You are able to interact with a number of the graphics like the house to turn “On” and “Off” the light as well as the sun and the moon to make it “Morning” or “Night”.