Leech and Amphetamine are specialized Mac utilities that, when I need them, perform so dependably I thank the software gods for them.
Amphetamine (Free) keeps my Mac awake when I don't want the system to sleep. It has a terrific array of options and preference settings; it can keep the disk alive while letting the display sleep, it will run only when a specific app is running, and it can even run in response to specific system events.
For the last month or so, I've been uploading files to BackBlaze via our trembling DSL line. Before I close up shop for the night, I'll set Amphetamine to run for 12 Hours so the uploads occur while I'm sleeping.
Another time I use Amphetamine is when downloading large files, such as system software updates. I don't want the iMac to go to sleep during a big download only to wake back up the next time I log in and resume the download. Amphetamine prevents that annoyance from happening.
And speaking of downloading...I trust Chrome to download most of the middling files I run across or have to download, like PDFs and whatnot.
But when the use cases run to downloading large files or a large number of files, then I want to use a memory-efficient and dependable standalone program.
Enter Leech ($6) from Many Tricks Software. Leech offers a simple interface: simply drag the download link to the Leech window and the download starts. Drag several links to the window to queue them.
I used Leech recently to download a batch of .CBZ and .EPUB files related to a Humble Bundle comics package I bought. I simply dragged each CBZ download link to Leech, made sure Amphetamine was running, and went to bed. Doing that job in Chrome would have taken hours, maybe many evenings, and resulted in me crying and despairing of my poor life choices.
Like Amphetamine, Leech offers lots of customizations and settings while remaining small, easy-to-use, and utterly reliable.
And be sure to check out Many Tricks Software's other applications, of which I own my fair share.