Can anyone suggest an application of combinatorial optimization in real life? I am considering TSP(Travelling Salesman Problem), Minimum Spanning Tree, etc.
There are a lot of them. By example, most of the tasks related with Vehicle Routing and schedulling problems are combinatorial and include sub-problems that apply the trabevng salesman problem. Personally I have worked on some of such tasks and you can find in my reserchgate profile.
Most named problems (traveling salesman etc...) have had generations of super smart people working on them, and I would be a little surprised if a new aspect would emerge from a research project now. However, as the other reply suggested (Dr. Arzola-Ruiz) there are some good vehicle routing problems that have emerged nowadays from practical application. In logistics, last mile package delivery is important & interesting and can be very powerful if done efficiently. The bike-share balancing problem seems to provide many challenges. These are examples of problems where there is incredible opportunity to improve naive solutions. You can waste a lot money doing it badly. Good luck!
There are indeed many. As far as (spatial) networks are concerned, you can find for example optimal hub location problems (see the papers by M O'Kelly), or also problems for optimal spatial networks such as subways (what is the optimal shape of a subway ?). I guess that new mobility services such as bikes, etc also display some combinatorial optimization problems...