Here is my nomination:
3D volume and weight calculator for estimating the cost of 3D printed objects
https://codecanyon.net/item/stl-volume-weight-calculator/3073161
3D object viewer for online 3D printing service providers
awsmin
87
bitsgeo
88
CidCode
90
https://codecanyon.net/item/flik-timeline-wordpress-responsive-timeline-plugin/17409873
#1. Contact Form 7 Multi-Step PRO
#2. Facebook Messenger for WordPress