The Alternative PHP Cache (SPC/APCu) improves performance. The opcode cache uses shared memory and directly executes code from there, minimizing the amount of slow disk reads and memory copying at runtime.
One-Time-Username is the simple solution to prevent confusion in your community, since it blocks the use of previously used usernames, after they become available for others, e.g. due to deletion or after renaming of users. One-Time-Username also manages the list of blocked usernames for you, it will automatically unblock them after the configured amount of time!
Tim’s 2-Factor Authentication provides additional proctection for your users’ accounts. After login it ensures that the user himself sits in front of the computer by asking for an ephemeral security code!