This app was mentioned in 2 comments, with an average of 7.00 upvotes
https://www.reddit.com/r/Android/comments/1865c5/drivedroid_boot_a_pc_using_isoimg_files_on_your/
Bought for £0.80 when it was first released, still worth the current £1.89 all day long. Also, while not required, the donate version of Amplify.
edit: Conversely, looking through my bought apps list - what are your worst purchases? For me, Avia media player. Got it when I first got my Chromecast because the other apps were either lacking/buggy so I bought Avia and found that too was a POS. Really should've got a refund and looking at the reviews now - they're charging via a IAP of $4.99 for CC support.
Ugh.