Checklist

Attack
Service Exploits
Weak File Permissions - Readable /etc/shadow
Weak File Permissions - Writable /etc/shadow
Weak File Permissions - Writable /etc/passwd
Sudo - Shell Escape Sequences
Sudo - Environment Variables
Cron Jobs - File Permissions
Cron Jobs - PATH Environment Variable
Cron Jobs - Wildcards
SUID / SGID Executables - Known Exploits
SUID / SGID Executables - Shared Object Injection
SUID / SGID Executables - Environment Variables
SUID / SGID Executables - Abusing Shell Features (#1)
SUID / SGID Executables - Abusing Shell Features (#2)
Passwords & Keys - History Files
Passwords & Keys - Config Files
Passwords & Keys - SSH Keys
NFS
Kernel Exploits
Privilege Escalation Scripts