Two possibilities:

1) Export the frame as a still using the floppy disc icon above the preview window. Export using .png format.

2) Use a velocity envelope. Put a node on the frame before you want to freeze, and on the frame you want to freeze. Right-click on the node and choose "Set to . . . " Then enter 0.

Absolutely simplest way, if it really is the last frame of the video clip, is to go into the clip's properties and turn off looping. Then drag the end of the event out as long as you want and it will repeat the last frame.

i would be wary of turning the velocity down to zero if working with interlaced material.
What chien says works well, but i think the most flexible is to export the image as a still then transition it with a "flash"

Theres also a photosnapshot script which works quite well and u can do this at teh press of a button..

I love freezing last frames and have done it a lot in Vegas.

The problem with using the last frame of the clip and turning off "loop" is that if it's NOT the exact last frame - or if you change your mind - you either have to create a subclip or use some other method.

The problem with the Zero Velocity is if you also have other velocity issues (like a ramp down or variable velocities) if/when you change ANYTHING in the velocity keys, the last frame will not be the original you chose.

So - for me - the easiest way to do the freeze is to go to it in the preview window, then click the little Disc Icon and save the freeze frame. I usually make a special folder called FreezeFrames, where I store these shots. I personally save them as JPEG's.

I then immediately can access them from the Medai Manager, or from the FreezeFrame folder or from the Project Media.

That way, everything accessible and no matter how I jerk around the velocity in the "action" clip, I still always end up on the best freeze frame.

Hope this helps.