Helix. Instant startup. Minimal configuration required. Has all of the killer features I want from an IDE anyway.

EDIT: I assumed people would just research this anyway, but a more complete list of features I enjoy from Helix:

• very responsive
• modal editing
• declarative configuration file format (TOML, not Lua)
• language server protocol
• debug adapter protocol
• written in Rust so I am more likely to be able to submit a PR if I need to

Some cons (all known issues on github):

• no plugin API yet
• inline LSP diagnostics are overly intrusive and can overlap your code
• cold-starts the LSP when you start the editor, so you might need to wait for symbol queries in a large project