Legend (free) Iphone and Android - makes cool kinetic/animated text videos. The one issue is it seems to have been made for Vine videos and only exports 6 second videos. When making longer videos, I like using kinetic text for scenes where I don't have any good media like stock images and video. Kinetic text is also great for "pattern interrupts" to help keep your viewers' attention.
VMER Video Joiner (free) - Android - I'm not sure if it's available on iPhone - It quickly and easily joins videos. I make multiple 6 second videos with Legend the use VMER to join them into a single longer video when needed
Word Swag iPhone and Android $3.99 - Great for making cool text graphics, memes, quote posters, etc. I tried a number of free options and IMO you're much better off paying the $3.99 for Word Swag.
I connect my Android to my PC using USB and transfer the filed created by these apps to my desktop to use in other software programs.
What are your favorite free and cheap apps?