PPT - PowerPoint Presentations
File Juicer can extract images and sounds from from PowerPoint Presentations as ordinary image and sound files. You could use Microsoft Office 365 to open these files, but in many cases, the presentation is a slideshow of interesting images collected via email and on the web. Then, it is better to extract the images and show them with Apple Photos or Preview.
You drop the .PPT file on File Juicer and it will extract the images and save them in a folder ready for viewing, emailing, being imported into Photos.
Apple KeyNote
If the PPT file is a real presentation and you wish to edit and work on, you can take a look at KeyNote from Apple. KeyNote is a full featured presentation application and it is also available for iPad and iPhone.