Must-use add-ons with Zoho CRM

Must-use add-ons with Zoho CRM

As we know Zoho CRM has a solid collection of add-ons and plugins with which we can do almost anything.
I recently got to analysing and short-listing the top add-ons and integrations. Was able to cover most critical processes in the lead process: and integrating with marketing automation. 

The addons that were the top rated were: 
Marketo (for Marketing Automation)
Unbounce (for Lead gen landing pages)
SalesIQ (for Analytical sales insights)
Talkdesk (for Browser based call center)

Here's a Free eBook with  4 Must-Use Add-ons for Zoho CRM Users . Do you have any recommended plugins? Please mention below. Would love your feedback on the eBook