I'd like to highlight some lesser-known but lightweight and useful software that have made life that much easier.
Free to download and use. Pro version adds some extra features
Wordweb Lightweight thesaurus and dictionary. If you write anything
Old version 1.01 works fine with Windows 7 x64 and is free. The new version 2.0 is paid only but well worth the $10.
MetaGeek InSSIDer 3 True to its name, this is a Wifi troubleshooting tool for network geeks. It shows active wifi SSIDs and the strength of each signal, and whether or not there's overlapping. If you're in a crowded office and you wonder why you can't connect, check out this tool. Version 3 is the last free version, the newer version 4 is paid only but adds support for 802.11ac networks. Wifi Analyzer is something similar for your Android smartphone.
F.lux Changes the color tone of your screen so it won't blind your eyes when you're working at night. Twilight is something similar for your Android smartphone. Both are free.