7 turns of 3/16" copper tube, inner diameter 5.3", turn spacing 0.3". Flat pancake. Inductance 13 µH. Clearance from inner turn to secondary 0.5".
0.05µF 50kV. A series of two surplus Maxwell capacitors model
30561 0.1µF 25kV with following specs: 
Capacitance:
0.1µF 25kV
Rated peak
current: 5 KA
Max peak
current:
25 KA
Max ripple
freq.:
10 KHz
Max RMS
current: 25
A RMS
Max Dissipation factor: 0.3% @ 120 Hz
Inductance:
80 nH
Dielectric:
polypropylene and paper, oil is I.P.B.P.
4.33" diameter gray PVC pipe, 19.7" wind with AWG 26 enamel wire, 7 layers of epoxy paint. Secondary first turn 1.5" higher than primary pancake. Inductance 29 mH, self capacitance 8.3 pF, resistance 56 ohm.
I use two sizes: 3.15" diameter aluminium flexible duct,
11.4" outer diameter, 12.7 pF 3.93" diameter aluminium
flexible duct, 15.7" outer diameter, about 17 pF
mounted 1.6" over the secondary top.
Made of two MOTs (Microwave Oven Transformers) and two voltage doublers, output about 8 kVAC, limited to about 0.3A. A third MOT primary (with shorted secondary) is in series with the 2 MOT primaries on the 220V side to work as a shunt.
550 pF 40kV capacitors (2) from tank terminals to ground and 3 mH toroid inductors (2) in series with the tank terminals. Capacitor and inductors are both home-made.
A network of capacitors (doorknobs are hard to find in Finland!) and two 0.1 mH iron powder toroid inductors. Also a simple remote control (relay) is used. Please, see the schematics. Again, the inductors are home-made.
RQ (Richard Quick) static gap with blower. I built two of them inside sections of 4.33" gray PVC pipe: Type A: 0.7" copper pipe sections, 2" long, gaps of 0.0275". Two series of 2 gaps connected in parallel Type B: 0.7" copper pipe sections, 4" long, gaps of 0.02". Two series of 3 gaps connected in parallel
Using an angle grinder motor at 10500 RPM and tungsten electrodes, capable of providing 350 breaks/s. Please, see the related page.