Basic Stuff

Spot check site
Check footer, social and top-nav links to make sure they're wired up
Proof copy
Device & browser testing
Check misc default pages and make sure they don't look horrible (search, user login, 404, etc)

Drupal Stuff

Create & upload favicon if needed
Double check site title and email address
Add default meta info (Pull description/keywords from about page)
Check sitemap setup, add necessary view pages, test (after domain propagation)
Check for any module, theme or core updates. Install, if available.
Update forms w/ client email address
Add google analytics/tag code via dashboard
Check for content displays and views in need of scaled image styles
Update http->https Google Fonts import link in styles.css if necessary
Remove console.log() items from JavaScript
Create user account for client w/ editor role
Make sure editor has permissions to edit any new content types
Add any other special editor permissions, if necessary (new modules, etc)
Delete any dummy content pages (except for style guide)
Disable any unused content type links on "Add content" menu (CTA, Event, Team Member, etc)
Disable views for any unused content types
Log in as editor and test basic CMS functionality
Disable views UI on modules page
Enable page/block caching & css/js aggregation (config>performance)

Pantheon Dashboard Stuff

Backup dev environment
Push dev to test, and test to live
Enable billing on site
Add domain name(s) to “live” environment (not dev or test!)
Enable “scheduled backups” on live environment
Enable “scheduled backups” on test environment (just in case)
Review Pantheon launch check report for anything major

SEO Stuff

301 Redirects
Verfiy Google Analytics code
Connect Webmaster Tools to Google Analytics
Submit XML Sitemap in Webmaster Tools
Image ALT tags

All done?

Delete this checklist page!