Quoted from PinMonk:
Li'l Deadpool's target is massively used in the T-Rex quest to finish it. You have to hit it over and over.
The Mini Deadpool area will give you a pretty useless Frenzy mode after the multiball but the third mode is what you want. If you complete the third mode (I think it is called bounce) it will give you a playfield multiplier for the remainder of the current ball you are on. if you manage to get 100 weapons and this on same ball you could potentially get a 3x playfield for an entire ball which will open it right up for some huge scoring.
That area is also used quite a bit in the wizard modes too as well with the previously mentioned T-Rex quest.