Unity’s Tower Defense Template provides a working example of a tower defense game. This project will teach you an array of programming techniques to help you build a deeper and more complex tower defense game of your own. 

Tower Defense Template

Scene Setup for Tanks

Tank Creation and Control

Camera Control

Tank Health

Creating and Firing Shells

Game Managers

Audio Mixing for Tanks

2D Roguelike Setup and Assets

Level Generation

Unit Mechanics

Architecture and Polish

TanksTutorialSlideDeck-v1.pdf

Tanks! Tutorial

Originally recorded at Unite Boston 2015, this  series will teach you how to create a 2 player (1 keyboard) shooter game. You'll learn about simple game mechanics, integrating world and screen space UI, as well as game architecture and audio mixing.

Tanks 

2D Roguelike Official Forum

Learn how to make a 2D Roguelike game with this project.

Over the course of the project you will create procedural tile-based levels, implement turn-based movement, add a hunger system, and finally add audio and mobile touch controls. This video series was filmed in Unity 5, but is compatible with Unity 4.6 as well.