Puran File Recovery is an interesting undelete tool which consistently delivers more than you might expect.
The program doesn't just present you with a list of drives you'd like it to search, for instance: instead you're able to choose partitions, and scan RAW and physical drives as well as FAT/ NTFS file systems.
Regular scans are very fast, and can present their lists of deleted files as either an Explorer-like tree, or in a simple table. Whichever option you prefer, a Search box makes it easy to find the files you need, and a Preview window shows you a thumbnail of any image (or displays a hex dump of unsupported formats).
You might then recover any selected file in a couple of clicks. But again, Puran File Recovery delivers more. If the program is telling you that, say, a video file is 1GB, and it should be 2GB, then a "Recover with custom size" option should allow you to enter the correct figure. This option won't always be available - and if the file has been overwritten then there's nothing anyone can do - but there's at least at chance that it will help you recover more of your data.
If that's not enough then the program's low-level knowledge of more than 50 file formats should help it detect them more accurately. That's not so unusual, but what's different here is that Puran File Recovery allows you to customise this list with new formats. If you know that a particular file type starts with a particular set of bytes, ends with some others, has its size stored in the header somewhere, then enter that information here and the program will be better able to find those files in future.