It depends totally on your interest –
Web-
1. Web portals
2. Banking Systems
3. Enterprise Systems
3. Social Network
Mobile –
1. Game
2. Messaging App
Machine Learning & Algorithmic projects –
1. Computer vision
2. Recommendation Systems
3. Search Engine
Real Projects –
1. Pick up and Open Source project and work on real world big projects and learn directly from experts from other parts of globe.