(Note this section may well be considerably expanded following further research by the author.)
There are now a few commercially available transistors on the Market which can switch many tens of kV. There are also a few transistors about that can handle pulsed currents above 5kA. These devices may match for example Krytrons and Sprytrons in terms of electrical performance, but not in terms of size and (in the case of the Sprytron) radiation hardness.
Thyristors are widely available in designs that can handle upwards of 10kA pulsed at several kV. They are however very slow switching devices and are not capable of achieving even low microsecond switching speeds.
A new class of devices is at present showing great promise in the R&D sector. These devices are optically (usually LASER) switched devices employing GaAs or Diamond film technologies. The reader is advised to consult the appropriate reference below for more information relating to these devices.