It is true that plugins may make your WordPress website load slower than expected but it is also true that only plugins can extend the functionality of a WordPress site. In fact there are some plugins will rather help your site run faster and more efficiently. Plugins I’m going to list below are used my site and I have installed and configured them in various other WordPress sites as well, so you can say that they are tried and tested!
Download URL: https://wordpress.org/plugins/akismet/
Spam comments are unavoidable in any WordPress website, though there are a number of spam filtering / blocking plugins available but Akismet is the most reliable and effective.
Ultimate Google Analytics
Download URL: https://wordpress.org/plugins/ultimate-google-analytics/
All in One SEO Pack
Download URL: https://wordpress.org/plugins/all-in-one-seo-pack/
As I have mentioned in my other post Yoast may be the most popular WordPress plugin but it bogs down your site significantly and results are not as great as claimed. All in One SEO Pack is the plugin I would recommend as reliable and effective.
Google XML Sitemaps
Download URL: https://wordpress.org/plugins/google-sitemap-generator/
Use Google Libraries
Download URL: https://wordpress.org/plugins/use-google-libraries/
This plugins helps your WordPress site much faster if you are using a theme with lot of jQuery which is the case for most of the themes (especially premium themes).
W3 Total Cache
Download URL: https://wordpress.org/plugins/w3-total-cache/
As per Wikipedia definition… “A web cache is a mechanism for the temporary storage (caching) of web documents, such as HTML pages and images, to reduce bandwidth usage, server load, and perceived lag.”… Which means a user doesn’t have to re-download all media / files every time someone visits your site, initial loading time may be long, but every consecutive page loading will be much faster. W3 Total Cache is a very good plugin to serve the caching needs of your WordPress site but use it with the help of somebody technical as this plugin may act vicious to some other plugin like Google XML Sitemaps.
Contact Form 7
Download URL: http://wordpress.org/plugins/contact-form-7/
This is the best free Contact Form plugin for any WordPress site. Gravity Forms is the best premium plugin in this category (which is used in my site), you can check out Gravity Forms Demo (username: demo, password: demo).
Download URL: https://wordpress.org/plugins/digg-digg/
Simplest social sharing floating bar for your WordPress site, lightweight and doesn’t bog down your site.
Really simple Facebook Twitter share buttons
As the name suggests it is really simply and lightweight compared to its competitor plugins, it serves the purpose of social sharing above and / or below the post / archive page / category page, etc.
This is plugin gives you more control over your WordPress site, shows all kinds of IDs by adding an extra column called Id.
Disqus Comment System
Download URL: https://wordpress.org/plugins/disqus-comment-system/
Not among my list of WordPress plugins and I have already removed it from my site as it was playing tricky with the CSS of my theme but lot of people recommend it as it helps to promote your site socially by means of a social commenting system.
Well this was my world of WordPress plugins (except Contact Form 7 and Disqus Comment System), hope it helps you chose plugins for your WordPress site.