Resistor between input and output for push-pull follower
Depending on the type of transistors, there might be an input voltage (usually around VCC/2), where both transistors are not conducting because the Base-Emitter voltage is not big enough to turn them on. This is the dead zone and because there is no transistor conduction, the output is fully floating, meaning that it can reach any voltage between VCC and GND if the input impedance to the following circuit is very high. 

The 100 Ohms resistor eliminates this dead zone because it forces the output near the input voltage.