Shotcut is a free, open-source and cross-platform video editor.
The program uses the popular FFmpeg to import source files, which means there's no need to worry about format support: it'll open just about every video variant that's ever existed.
There's also support for capturing resolutions up to 4k from SDI, HDMI, webcam, JACK & Pulse audio, IP stream, X11 screen and Windows DirectShow devices.
A straightforward interface ensures you'll be up-to-speed immediately, and offers plenty of ways to customise your working environment.
There are lots of video filters, from simple colour/ brightness/ contrast tweaks, fade ins and outs, transitions and so on, to special effects, video compositing and blending modes, chroma key, HTML overlay and more.
Shotcut offers almost as many audio effects and filters, with fades, balance, bass and treble, band pass, delay, downmix, normalize, pan, reverb and more.
All this is editable on a highly configurable multitrack timeline, then exported in whatever video format you need.
18.06.01 adds (see changelog for more):
Many bug fixes due to introduction of keyframes and change to memory management in v18.05.
Added simple and advanced Keyframes to the Blur and Mask filters.
Added seek buttons for simple Keyframes.
Added ability to add and remove advanced Keyframes using double-click.
Added ability to drag advanced Keyframes to adjust both value and position.
(When dragging, hold down Ctrl key to adjust only value or Alt key to adjust only position.)
Added double-click to toggle simple Keyframes controls (circles).
Added double-click to toggle fade in/out controls (circles) on Timeline clip.
Added many animated (keyframes) presets to the Size and Position filter.
Added Reverse to clip Properties menu.
Added Detach Audio to timeline clip’s context menu.
Added 5.1 surround support to the Copy Channel and Swap Channels audio filters.
Added caution message to GPU Effects confirmation dialog.
Added a Keyboard Shortcuts link to the Help menu.
Changed presets file format to YAML.
Changed Settings > GPU Processing to GPU Effects.
Reduced memory usage on 32-bit builds (by constraining multi-threading).
Upgraded FFmpeg to v4.0.
Integrated AMD AMF hardware-accelerated H.264 and HEVC encoders on Windows (Set Export > Codec to h264_amf or hevc_amf. Requires recent Radeon or AMD APU.)
Upgraded MLT to git master (v6.8.0 minimum required to build).