As I've grown in this pursuit, I've come to appreciate some of the possible improvements to telescopes as they typically arrive from the vendor.

   A basic Pimpage Package for my scopes includes:

    --A Williams Optics Dielectric diagonal to improve light transmission

 --- A 8 or 9x50 Right Angle Finder for good and convenient views in my light polluted skies.  Having the same finder on all my scopes also allows an intuitive grasp of angles, magnitude, and orientation, speeding up object locating.

   I just recieved a laser pointer (5mW), and am awaiting a bracket for my 12" Dob.  If it works like I expect it to, this might make it onto the list for large Dobs.  I find initial pointing of this beast to be a bit like trying to aim a pickle barrel!

  What "must haves" do you add to your scope?  Why?

Besides the laser and a Telrad, I have found heaters to be invaluable even in the summer. A secondary heater on the DOBs and a primary objective heater on the refractor. When it hits dew point here and everybody else is packing their equipment up, agroup starts to form around me as I am still going strong. 

These work great for newtonions: Heaters

Another great thing is a two speed Crayford focuser. For very high power focusing a electronic focuser is also nice.

JJ 

  Cool ideas JJ-

   I've just got to say, you are HARD CORE.

A motorised focuser is a "must have" IMO and Heaters for the optics are real life savers when weather can lead to dewing or frost.  

Excellent choices. I won't try to be too terribly specific with the name brands but will answer based off the actual items that I use most often. I will skip all the astrophotography equipment and keep on focus with the visual observing.

1) Binoviewer (absolute must-have). It is the single most important item I use for visual observing.

2) RA Finder  Saves from breaking your back or pulling a kink in your neck. Also, is easier to use in the sense that objects are not reversed.

3) Barlow Because it all depends on what a scopes aperature is and focal length I will not give any particular magnifying power. Just the fact that everyone should own one.

4) Solar filter  The sun is the closest star. Even on a day with some clouds you may still see the sun poke through at times. The planets, stars, galaxies ect...do not have enough light to pop through even a light cloud cover. With the sun, having a light wisp of clouds actually makes the view even more interesting. Not only that but you can use your scope in daytime (and everyone really enjoys the stares neighbors give you when you stare at the sun), see transits, sunspots and granulation on the surface. With Ha filters you can actually see the sun in real-time motion.

5) Variable Polarizing Filter Excellent all around for brighter planets, the moon at all different phases and even the sun with a filter. The abilty to change how much light actually is rejected (from 1% to 40% light transmission) makes this useful in any # of situations.