Pete Lozzi, a Mac guru and frequent speaker at https://www.macnexus.org, The Sacramento Macuser Group, says
All the virus programs, MalWare Bites, Kapersky, McAfee, ... and clean-up programs, MacKeeper, CleanMyMac, Disk Doctor ..., are really spyware.
They make more money by selling information about you and your browsing habits than they make from selling software. They may generate reports about how many problems they have scanned for, but that's about all.

The main utilities I use: Time Machine - backup
MalwareBytes - Virus and other malware
EntreCHeck - comprehensive diagnostic report on the current state of your computer.
SuperDuper - Create bootable system backup

Notation: [R] R = VersionTracker user rating 1-5
[R1, R2] = Rating current version, previous versions
{R} - MacWorld Rating
The number of downloads indicated populatairy.

GraphicConverter Classic 5.7.5

# Imports about 170 graphic file formats

# Exports about 45 graphic file formats

# Browser

# Batch conversion with additional actions

# Slide show

# Easy creation of optimized images for the internet

# Basic images manipulation

# Enhanced images manipulation

DiskWarrior

VirtualLab Data Recovery [3,1] - Data Recovery Software for Deleted files,
damaged or missing volumes 

Toast 7 Titanium {4.5} - CD / DVD burning

textexpander http://smilesoftware.com/


www.rogueamoeba.com/airfoil/mac/
Send any audio from your Mac to AirPort Express units, Apple TVs, iPhones and iPods Touch, and even other Macs and PCs, all in sync!

VLC media player  www.videolan.org/
VLC is a free and open source cross-platform multimedia player and framework that plays most
 multimedia files, and various streaming protocols.
 
handbrake -  HandBrake is an open-source video transcoder available for Linux, Mac, and Windows.
 Everyone can use HandBrake to make videos for free. HandBrake is a post-production tool.
  Its primary purpose is to convert videos from supported source formats to MP4 or MKV format.
  
  Using Screenshot in the QuickTime Player app, you can make a video recording of your computer
   screen. You can open the recording in the app and save it on your Mac.
  
ecamm.com/mac/callrecorderft/  Call Recorder for FaceTime

SutffIt [3,1]- compression.

SMARTReporter 2.0.1 - can warn you of ATA hard-drive failures before they actually happen!. If you want S.M.A.R.T. support for your FireWire hard-drive, send feedback to Apple. http://homepage.mac.com/julianmayer/

Run Windows on an Intel Mac:

iStat Menus, a Mac app by Bjango - CPU, Disk, battery status

flip4mac - Run windows media player in quicktime

Hand Brake -
Jack the Ripper

Temperature Monitor [4]

ThermographX [4.5]

Battorox 1.8.1 [5]

Entourage Email Archive X [5]

Process Microsoft Outlook winmail.dat files
Letter Opener (OMiC) - Processes in Apple Mail
TNEFŐs Enough - Stand alone
tnefDD Sourceforge

iPhoto Library Manager 3.1 [4,5]

LaunchBar 4.0.2 [5] {5} - aunchBar is an award winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the web. It provides instant access to your applications, documents, contacts and bookmarks, to your music library, to search engines and more, just by entering short abbreviations of the searched item's name.

TinkerTool [5] Alter system settings, add translucent terminal windows, and display hidden files and folders.

PGP Desktop Home {4.5} - PGP uses public-key cryptography to enclose your documents, e-mail messages, virtual disks, and instant-message (IM) sessions in a so-far unbreakable wrapper..

QuicKeys X3 3.1 {4} At $100, QuicKeys 3.1 is quite expensive for a utility, and creating complex shortcuts still takes diligence that may also require a trial-and-error approach. But you'll save time and sweat by using QuicKeys to automate repetitive tasks.

Others from jheary post on networkWorld blog

• -Adium IM
• -VirusBarrier X5 (come on I'm a security guy, I don't buy the MACs are secure hype)
• -MAC Pilot - gives me access to all the hidden MAC nerd knobs in a easy GUI
• -Default Folder X - It gives a bunch of flexibility to open and save dialogs (still figuring this one out but I can see the benefits already)
• -DropFix - A free and very slick image resizing and conversion tool for my blog images.
• -Metasplot Framework - Can't live without it for IPS (Intrusion Prevention System) and CSA (Cisco Security Agent) demos. Runs much better on MAC OS than Windows.
• -Ettercap for MAC - security swiss army knife
• -Flip for MAC - Allows me to view WMV (Windows Media Video) videos in quicktime. Works great!
• -Rapid Weaver - html and blog authoring software. Haven't had a chance to learn yet.
• -RDP client to connect to windows boxes
• -Cisco IPSEC VPN (Internet Protocol Security- Virtual Private Network) Client
• -Cisco anyconnect SSLVPN (Secure Socket Layer VPN) client
• -Little snitch - outbound connection monitoring and control
• -KisMAC - wireless stumbler and cracker
• -Several dashboard widgets
• -Proxify - to get though annoying URL filters
• -accuweather ski report - gotta know when it's a powder day!
• -Yellow pages widget

Weekly Maintenance:
Macjanitor
YASU
Cocktail ( $14.95 shareware)

Timbuktu Pro 8.5 {4.5} - Macintosh remote control.

Dave 2.5.2 from Thursby (TSS) Network with PC using TCP/IP