iMountX allows you to mount and unmount volumes of different types such as USB or Firewire. The application is very simple so you will not need any help to use it successfully.
When you run the tool, it automatically checks for connected devices. Its interface is straightforward with no hidden options. It displays the names of the volumes that have been recently mounted. It also shows their identifier and their current status. Two very simple buttons allow you to mount or unmount the selected volume depending on the status. In case of any changes in the system, for example, connecting another device, you can use the Scan button to update the list.
In general, iMountX does not do anything that you cannot do from Terminal; however, it saves you from memorizing and typing the corresponding commands. Compared with other similar applications, this tool has several limitations. In my opinion, its most serious drawback lies in the impossibility of managing network or cloud volumes. The product is completely free and can be downloaded from the developer's site.