I thought it would be interesting to find examples of really clever experimental techniques.
So not not necessarily experiments that have produced important (or difficult) results. And not just examples of really advanced technology. But experiments that used clever "tricks" to eliminate errors, cancel out other effects, or just to make the effect visible in the first place.
One example is Pound-Rebka: this used Doppler shift to cancel out gravitational time dilation of gamma rays from the top of a tower. They then did the experiment again with the source at the bottom of the tower. By subtracting the two results, they doubled the measured value (and probably cancelled out some noise).
Any other favourites?