The following are various tools I use for work or in my home lab setup:
GNS3: Need to simulate a network? GNS3 works well.
HP USB Disk Storage Format Tool: Can be downloaded from CNET and allows you to format more drives, not just HP. If you have trouble formatting your USB drive this is a simple tool to use before you try putting an image on it with UNetbootin.
PuTTY: A must have tool for telnet and SSH, free and open source. Great for connecting to ESXi hosts, or various other devices.
UNetbootin: used for creating “live” bootable USB drives. Great for running ESXi from a USB drive or just installing from a USB drive. Easy to use and free!
WinRAR: Need to extract something like an ISO image? WinRAR will do that and much more. In my opinion it is far superior over winzip and other tools alike.