at

Out of the box, at works in such a way that it's SUID&SGID daemon (default perms is 6755):

-rwsr-sr-x daemon/daemon 50456 2010年07月28日 12:49 usr/bin/at

When a user runs the at command to schedule something, at writes that to /var/spool/atjobs/:

-rwx------ 1 pyllyukko daemon 4741 Dec 7 09:37 /var/spool/atjobs/a00008016899aa

at supports access control through /etc/at.{allow,deny}. The default is, that there is a blacklist of users in /etc/at.deny.