I am curious as to the shutter speed of fast action. I will be filming a martial arts short soon in 24 fps, and was curious as to what shutter speed is best to make the action look more frantic. I know 1/48 should be used for regular scenes like the conversation...tension builders...but what about the action? I know its not standard but more artistic preference, just looking for a guideline to try out. Also would mixing the 2 shutter speeds be ok on the eyes?

Mixing shutter speeds is fine. Available lighting will be the issue for increasing the shutter speed to get that frantic look. 1/600 to 1/1000 is a good starting point if light is low. Over 1/1000 is where you probably want to be. If there is too much light, just ND.

is it really that high? I can notice a difference at like 120 (err i think thats in 24), does it have to be 1/1000 to be that drastic?

Well, it depends on how sharp and frantic you want it to be.
I like over 1/1000. If the fight scene is in the rain, you see the individual drops. Blood looks badass too.
Lighting is the key issue here so you have to get all the production factors together and figure out how you want it to look. There are no rules, it's a purely creative issue based upon the scene and available light.

yea thanks. The light will be daylight in the forrest of skeleton trees (without the leaves) so i guess i`ll just need to run some tests and see whats what.

1/1000 is very, very high. you can do it in daylight, but that's about it. I'm not saying that it won't look good, but certainly you can get that 'frantic' look from say 1/200 up. 1/150 maybe.