Extension:LastUserLogin

The LastUserLogin extension displays a simple table of users and the last time they logged in. This can be useful, if your wiki is used as a knowledge base for outside personnel. If you have a requirement that they check the wiki prior to placing a call or email LastUserLogin can be used to verify that this policy is being enforced.

User right
This extension provides a the userright  which is by default assigned to the sysop group.

Impact to other functions
Adding a log entry for every user login impacts the script /maintenance/removeUnusedAccounts.php as the script checks for the number of page-edits, image-uploads and log-entries. However you can patch removeUnusedAccounts.php to ignore the first login which is very common for spamming robots:

original

change to that