1st: Philips SL*
2nd: Osram HQI-BT 400W/D
3rd: Philips MHN-TD 70W
4th: Philips MH-T Artcolor

Well. That's tough. My current love affair is with different colored MH lamps of multiple makes and shapes and powers. Never cease to impress with their color combinations when running up and steady lit. They are simply addictive . SDW-T and SDW-TG white sodium lamps are cool for sure and I like that red-rich light. Good old classic Philips CDM with /942 color set the standard 25+ years ago and is probably not bettered even today. Neon sign tubes are just unlimited field for creativity... Small cute deluxe mercury bulbs are a perpetual love, too... 

Unfortunately, I have not seen SDW white sodium lamps with my own eyes.

That is a tough one?, I favoured whatever I was using at the time, but of all the lamps I’ve used, the one I have always come back to is the lighting industry changing electronic CFL 

My favorite are these C7 Christmas/Night/Indicators Light Bulbs

Perhaps my preference will not be popular, but I have to go for gas-cooled LED filament lamps!

Their insanely high luminous efficacy tops all traditional lamps and traditional LEDs, the colour rendering properties are truly outstanding when well engineered, the light distribution is omnidirectional, their lifetime reliability is unparalleled, the appearance matches my preference for how a lamp should look - and when they fail, they are easy to replace without having to throw away the luminaire.  During the past decade it was a shame to see so many traditional lamp designs disappearing, but the invention of LED filaments in gasfilled bulbs has the potential to keep at least some of their formats alive.  Whether one wishes to replicate the properties of incandescent GLS, halogen spotlights, linear fluorescents, or large-envelope HID lamps in the lower wattages, LED filaments are doing a rather good job.

If I had to choose some traditional lamps as well, it would be SOX because my first job was involved in their engineering, self-ballasted mercury because of the fiercely complex interactions between the filament and arc tube which makes their design optimisation so complex, and short arc metal halides because I love the advanced chemistry that governs their performance at such high temperatures and pressures.  But aside from lamps I also like designing mechanised production processes, and then I would have to add GLS and LFL because there is almost nothing in the world that beats the mechanical beauty of the high speed machinery required for their cost-efficient mass production.

Yeah, I would agree here, they would be my second choice, invented by the Japanese and then perfected by the Chinese, the micro engineering that goes into LED filament lamps is really impressive! 

My favourite would have to be the linear fluorescent lamp, the huge range of control gear, luminaires, colours and applications they found in their prime was quite impressive.
You would struggle to find anywhere that didn't use them at one point: shops, offices, factories, warehouses, schools, buses, trains, RV's, ships, planes, homes and garages to name a few, and then the different varieties that were used in those applications with T5 short, T8 and T12 in triphosphor and halophosphor and then T5 HE/HO featuring later on.

The external ballasted CFL (2D, TC-S, TC-D, TC-T & TC-L etc.) comes a close second place, with all of the new luminaire designs they allowed where LFL could not be used, giving fluorescent even more uses in more decorative luminaires and security lighting.

My set: SDW-T, SDW-TG, CDM WARM, COB LED and other technologies too.

I don't really have a favorite. All I care about is if the lamp works well, lasts a long time, and doesn't use way too much power.

LPS all the way, I love them all, particularly linear SLI/H lamps. Their start-up colour is out of this world

For me, my favorite light sources are non-integrated CFL lamps, bipin and RDC base linear fluorescent tubes, circline fluorescent lamps, mercury vapor, high pressure sodium, metal halide (quartz and ceramic), and low pressure sodium lamps (SOX, SLI/H, SO/H, and SOI/H).

I like any gas-discharge or incandescent lamps. Mainly High Pressure Sodium, Low Pressure Sodium, Coated Mercury Vapor, and Ceramic metal halides.

for me it is MORE the "use" and the "space" it is in
but to answer the question Discharge HID lamps like SON and MV/MH - I am fascinated by the "new- high tech" lamps that got snuffed out by the L*D like induction and white SON and Metropolis lights
LOVE the classics like SOX and incandescent