There are some tools that make my job as a Product Owner much easier. My Top 10 and a bonus one:
Jira – a very powerful tool for managing the backlog. There are plenty of integrations and extensions available.
Balsamiq Mockups – for sketching user interfaces. Many UI elements ready to drag & drop and you can add your own too.
Proto.io – for creating fully interactive hi-res prototypes, which can be tested on any device and look & feel like a real app. Great customer service.
Lucid Chart – an easy way of creating and sharing flowchart diagrams.
Evernote – for taking notes (and much more). Notes can be combined with images and other UI elements. Works on any device as an app and as a website. Excellent speed of search.
Trello Board – great for to-do lists, sharing ideas and roadmaps. Might be even used as a backlog. Works as a website and an app.
Slack – a tool to organise team communication into channels. Great for remote teams.
Dropbox – for storing and sharing files in the cloud. Works on any device and synchronises seamlessly.
Prezi – to wow the audience with animated slides. Many templates ready to use.
Pixelmator – powerful, easy and beautiful image editor for Mac.
Documents, spreadsheets, slides etc.
Google Apps for Work – for creating any kind of documents. Simple and easy to share, available from anywhere.