Amending changes in a commit without modifying the message

git commit -a --amend --no-edit

Displaying only the files modified in a commit

git show --pretty="" --name-status <commit-ref>

Browsing the repository on a local web interface

git instaweb

(It requires lighttpd or other httpd daemon. Props to Cool git commands for this one.)

Search git history for a specific string

git log -S '<searchString>'

Bring a file from a specific commit

Useful when you want to try everything with the content of your current state, but you want a file/folder to have contents of a specific commit.

git checkout -- <file-or-folder-path>

Update submodules to the latest branch they’re tracking

git submodule update --recursive --remote

Check references where the main branch has been for the past 2 weeks

git reflog main@{2.weeks.ago}