Paragon Software has created an app for Android that allows your device to natively read partitions in file systems that Android normally can't handle, such as Microsoft's NTFS, allowing immediate and easy use of any USB drive or external hard drive. Unfortunately, you can't use the app to work with files on a Windows computer directly via your Android device. It's worth noting that this app works in a read-only fashion, which means that you can pull the files onto your device to work with them, which converts them into whatever file system your device uses, but you can't modify them directly on the flash drive. Likewise, you can't write files to flash drives formatted in non-native file systems.
The most obvious use case for this app is having an NTFS flash drive or USB hard drive sitting around, but no computer to plug it into. It's also useful to check out the contents of mysterious flash drives or USB hard drives that you don't want to plug into your computer for fear that they may contain viruses or malware. Using a USB enclosure for a dead computer's hard drive in order to salvage the files is also a helpful use case for this app, if you either don't have another computer that you can stick the drive into, or simply want to transfer the files directly onto your phone. Along with Microsoft's NTFS file system, the app can work with HFS+, the default file system for older Mac computers. The app can work with FAT32, a common file system for MicroSD cards and some older computer systems. It cannot work with the EXT and SWAP file systems commonly used in desktop GNU/Linux distributions, but most phones can read those natively due to Android's Linux kernel core.
If there's a functional computer around that can use MTP, there's not much point to this app while you're near it. If you commonly work with files on the road and don't always have your laptop, however, it could be a lifesaver. Unlike some of Paragon Software's apps, this one does not rely on an in-app payment for useful features, and you should be able to download it for free using the Google Play button below and immediately take advantage of its full feature set.