elementary OS

General

App launcher

`⌘ Cmd` + `Space`

All hotkeys for elementary OS

General App launcher	`⌘ Cmd` + `Space`
General Window switcher	`Alt` + `⭾ Tab`
General Swtich windows backwards	`↑ Shift` + `Alt` + `⭾ Tab`
General Window overview	`⌘ Cmd` + `W`
General Window overivew (across all workspaces)	`⌘ Cmd` + `A`
General Switch workspace	`⌘ Cmd` + `← →`
General Workspace overview	`⌘ Cmd` + `S`
General New workspace	`⌘ Cmd` + `0`
General Jump to specific workspace	`⌘ Cmd` + `1` - `9`
General Move app windows left and right between workspaces	`⌘ Cmd` + `Alt` + `← →`
General Move window with workspace	`↑ Shift` + `⌘ Cmd` + `← →`
General Maximize / unmaximize window	`Ctrl` + `⌘ Cmd` + `↑ ↓`
General Lock screen	`⌘ Cmd` + `L`
General Move window	`⌘ Cmd` + `Mouse movement`
General Resize window	`⌘ Cmd` + `Mouse movement`
General Shift	`⌘ Cmd`
General Shift	`Win`
General Shift	`↑ Shift`

Similar combinations for other applications

RStudio (Mac)

Attempt completion

Completions (Console and Source)

`⌘ Cmd` + `Space`

Corel Painter (Mac)

Zoom tool (zoom-in)

Panel menu commands

`⌘ Cmd` + `Space`

IntelliJ IDEA (macOS)

Open quick definition lookup

Navigation

`⌘ Cmd` + `Space`

iPad Smart Keyboard

Spotlight Search

General

`⌘ Cmd` + `Space`

Apple macOS

Show or hide the Spotlight search field. To perform a Spotlight search from a Finder window, press Command + Option + Space. If you use multiple input sources to type in different languages, these shortcuts change input sources instead of showing Spotlight

Cut, copy, paste, and other common shortcuts

`⌘ Cmd` + `Space`

Xcode

Show or hide the Spotlight search field (when multiple languages are installed, may rotate through enabled script systems)

Other system and application shortcuts

`⌘ Cmd` + `Space`

Adobe Acrobat 2017 (Mac)

Change whether the row with focus is in the selection

Working with PDF Portfolios

`⌘ Cmd` + `Space`