The default Second Life viewer is a good pick for those who want to explore and play Second Life in its full environment. Contains the last tools and options that Second Life has to offer.
A less laggy version of the Second Life default viewer making it a better fit for those who has older computers. Holding the lowest crash rate of all the Third Party Viewers this is a good option if you do not want to loose all of what the virtual world has to offer in a more comfortable and easy way to access all the SL features.
"Catznip aims to refine and reinvent your window into Second Life. Our focus is stability, usability, privacy and plenty of new original home grown features. It's about taking a fresh look at things and attempting to do them better.Catznip is the development viewer for the alternative implementation of the RLV specification."
This viewer is one of the best options you have if your into SL combat. Singularity Viewer is still loyal to the classic user interface but yet holding all the needed tools to make your SL enjoyable roleplay wise.
Exodus Viewer is the jaguar of third party viewers for gamers. Filled with enhanced options to make your combat more thrilling counting always with a maximum performance. The format of this viewer is side by side with the Second Life Viewer 3 but expect to see more cool features! If you have a top of the line computer and you pew pew all the time..this viewer is for you.
"A Viewer aimed at High-End users for Photography and Machinima, featuring some of the most important updates, and always strives to be as most up to date as possible with a lot of updates, recommended for users that don't fear downloading a new version every week, day and sometimes even hours"
"The Dolphin Viewer is a viewer for virtual worlds, based on the official Linden Lab source code, that contains many fixes and enhancements for builders, explorers, sailors, and other vehicle enthusiasts."
"It is primarily intended to be used by BDSM fans with BDSM oriented objects in-world, which are able to restrict the user from detaching items, receiving IMs, hearing chat, teleporting etc. It can also be useful for totally PG purposes, such as forcing to teleport somewhere (facilitating transport networks), changing the Windlight settings through scripts (helping sim owners), preventing from teleporting out of a maze, etc."