This is truly one of the most useful lists of tricks for features you can add to your WordPress Function .php file.
The list includes the tricks to:
Add Google Analytics Code (This is useful if you are using a child theme and can’t access the header file.)
Add a Favicon to Your Blog (that is the tiny little image that shows up next to the name of the page in the tab and address bar on your browser.)
Add a Custom Dashboard Logo (shows up on the dashboard, this can be useful when you are creating a theme for other to use or when you have multiple users who log in to your WordPress site.)
Change the Footer in WordPress Admin Panel (This may come in handy if you can’t find a simple method of changing your footer.)
Add Custom Dashboard Widgets (Ooo…this way you can add your own widgets that you have written that compliment your theme!)
Change the Default Gravatar (Simplifies the process of having a branded avatar when you post on other blogs instead of having the mystery man or the weird alien.)
Dynamic Copyright Date in Footer (Have you had your website since 2005 but your footer says “copyright 2011”? Well this handy little bit of code will let you show the world that you’ve been around a while. It will change it to “Copyright 2005-2011” by pulling the dates from your earliest and latest posts. Pretty cool!)
Control When Your Posts are Available via RSS (This one should come in handy for those of us who don’t always use the “draft” button as we should! It will put a delay of several minutes on your RSS feed so those notorious errors you see immediately after hitting “publish” can be corrected before the world gets to see them!)
Customize Excerpts (These tips give you more control over how your blog excerpts appear. You can change the … at the end and control the length of your excerpts.)
There is more, but those are the ones that I think you might find the most handy. To get all the directions and see the rest of the tips, check out the full post at WPBeginner.com: 25+ Extremely Useful Tricks for the WordPress Functions File.