This bash “one-liner” displays the 10 largest blobs in the repository, sorted from smallest to largest. In contrast to the other answers, this includes all files tracked by the repository, even those not present in any branch tip.
It’s very fast, easy to copy & paste and only requires standard GNU utilities.
git rev-list --objects --all \
| git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' \
| sed -n 's/^blob //p' \
| sort --numeric-sort --key=2 \
| tail -n 10 \
| cut -c 1-12,41- \
| $(command -v gnumfmt || echo numfmt) --field=2 --to=iec-i --suffix=B --padding=7 --round=nearest
The first four lines implement the core functionality, the fifth limits the number of results, while the last two lines provide the nice human-readable output that looks like this:
...
0d99bb931299 530KiB path/to/some-image.jpg
2ba44098e28f 12MiB path/to/hires-image.png
bd1741ddce0d 63MiB path/to/some-video-1080p.mp4
For more information, including further filtering use cases and an output format more suitable for script processing, see my original answer to a similar question.
macOS users: Since numfmt is not available on macOS, you can either omit the last line and deal with raw byte sizes or brew install coreutils.