Simple answer: if it's not in Equivalent Time (ET) sampling, it's doing it real time, and a SINGLE or NORM trigger will capture the event, when set up correctly of course.
AFAIK, all mainstream scopes these days are real time (100MHz BW with 1Gsa/s or so sample rate). Older scopes (usually), with ET sampling, are still fine for single shot events, but only up to the sample rate where ET kicks in.
Analog scopes can also be used for single events, but unless you have a good eye, you'll want some storage mechanism... a storage CRT, or a mounted camera (put the camera in front of the CRT with the shroud, open the shutter, expose the event, then button it up and send it to the photo lab..), or a digital camera with long exposure. This also helps if you have a slow but repeating signal.
Here's an example of a xenon flash tube light pulse (or rather, several) I recorded on a Tek 475 with 15 second exposure:
3 x 50us of trace, out of 15,000,000us of exposure time, isn't too bad for a reasonable quality image.
Curiously, the earlier digital scopes did real time sampling on broadly similar time scales (I think the HP 54600 was around 10us/div fastest real time).
Tim