WordPress Admin Theme Plugin makes clean and simplified wp-admin dashboard.
WordPress Optimize plugin cleans up the site’s database and helps save bandwidth.
WordPress Donation plugins allow the visitor to donate and allow you to accept online donations.
WordPress Sitemap Plugins allows you to create and add a Sitemap file to Google Webmaster Tools.
WordPress invoicing plugins allow you to create professional quotes and invoices that client can pay for online.
Landing Page plugins let you create a quick homepage for your website. Mostly this plugin allows you to create a website with easy drag and drops feature.