iFunny is a social media application primarily used on mobile devices. iFunny should be avoided as a source for images as they heavily compress all of their uploaded media.
You would typically want to use this tag when there is an iFunny watermark at best, or 3rd party watermark at worst.
Artists will typically and intentionally include the iFunny watermark in a media piece they create as part of a bigger meme.

An example of a watermark would look like the following image:
post #3316500

Another proper use of this tag is displayed in the post as their character is wearing a shirt with the iFunny logo:
post #1649304

If the image is sourced from iFunny directly, the tag 3rd party watermark should be used as this service automatically appends their watermark at the bottom of picture media.

If there is no clear mention of iFunny on a piece of media, and the image was only sourced from iFunny, then this tag should be avoided.