ShareX is an open source screen capture tool with a very extensive feature list.

The program doesn't just grab individual windows and a full screen, for example. You can also capture rectangles, ellipses, triangles, diamonds, polygons or freehand shapes. There's support for multi-monitor systems, and even a screen capture tool to save desktop activity as an AVI or animated GIF.

Any image you might grab can be processed in many ways. You can crop, resize or rotate it; annotate it with lines, arrows, shapes, textboxes and more; obscure confidential details (passwords, say) with the obfuscator; customise it with a watermark, or apply special effects, including borders, shadows, torn edges and more.

Once you're happy, ShareX can directly upload your work to more than 30 online services, including Twitter, Flickr, Picasa, Photobucket, Dropbox, OneDrive, RapidShare and GoogleDrive. You get a module to create custom uploaders for sites which aren't in the list. And there are also more general options, like the ability to send a grab via email, or copy it to a shared folder.

Even now, the program hasn't finished. Once the capture has been uploaded, you can have ShareX do something with the link: use your preferred URL shortening service, post it on Twitter, send it in an email, maybe just paste it to the clipboard.

Best of all, this is extremely configurable. You might set your preferred file format, set up the effects you'd like to apply, define a precise format for the saved file name, launch a custom program to work on it, select multiple upload destinations (you're not restricted to just one) and more, then launch the entire process with a custom hotkey.

Note this is the portable version of ShareX.

What's new:

Region capture related changes:
Tab key or Mouse 4 button will swap between last region tool and last annotation tool
Redesigned Task settings -> Region capture tab to be more user friendly
All mouse actions (except left click) will be configurable from Task settings -> Region capture that way you can get same behavior as old region capture; for example, right click to cancel capture
Removed AnnotationEnabled setting because you can now have full control on each mouse actions
Region capture will remember last used region tool and open with it selected
Last used annotation tool will be also remembered so that way when you swap tools it will select last used annotation tool
When drawing tool is selected cursor will show border color and size, this is also useful to know is current tool is region rectangle or drawing rectangle
Allow drawing info text near cursor when magnifier is not enabled
When creating region you can hold Ctrl key to change position of region
When region is selected Ctrl key will move region instead of Shift for consistency with region create moving
Holding Shift will increase region resize or move speed by 10px
Holding Alt will allow to resize region from bottom right instead of top left
Menu key will open options menu
Double clicking when multi region mode enabled won't close it when there is no region to be captured
When creating region holding Alt key will more accurately and with better performance calculate close regions to snap
Added previous Region capture (Annotation) back as hotkey only which will be called as Region capture (Simple annotate) in hotkey settings
Added puush file uploader
Added Google Drive direct link option (by @mihe)
Added option to remember last drawing mode in Greenshot image editor settings window (by @campbeb)
Scale Greenshot image editor window size when icons are larger than default (by @campbeb)
Added option to maximize the Greenshot image editor window when it is larger than working area (by @campbeb)
In SFTP upload if file with same name is exist, truncate file before uploading
After capture tasks -> Show file in explorer and in other places where folder need to be opened with file, it will use already open Windows Explorer window instead of re opening new one (by @dannoe)
Hotkey settings and quick task menu reset to default buttons will ask for confirmation (by @dannoe)
Implemented Dropbox API v2
Option to use file extension for Hastebin syntax highlighting

Verdict

ShareX has a lot of features and functionality, and initially it can seem intimidating. The program is extremely configurable, though, and it's ability to automate just about everything will save you an enormous amount of time.