WordPress plugins are effective and easier to use. They do what they are meant to. You can get WP plugins for almost any tweak you want to do with your site. But there are still a few tweaks that can't be done by plugins. Or, if they could be done -- plugins might build seriously more load on your site. To solve this, you can always place some PHP scripts which run into your WordPress' site's front-end to offer wanted results. This process doesn't need installation of plugins and hence strengthens your site's security and keeps bloat away.
Here is the list of some highly useful PHP scripts to use for your WordPress blog. This list is expandable and will surely expand to larger number of scripts as time moves on. All the codes listed below are error-proof and tested by me on my blogs.