I am doing a cake where i need to have a grass looking effect, which tip is the most common for this type of design. Also is there a certain icing i should use that works best for designs like these also?

Wilton makes one I believe the number is 233. Medium to thin buttercream icing will work.

TexasSugar is correct... #233 grass tip.
Or the extra large grass tip #333.

Agree with the ladies above. I used that same tip on this cake...

http://stuffbystace.blogspot.com/2010/09/packers-football-cake.html

Is that the texture you are looking for?

I agree. I used the same tip and it works great! Check out my golf cake.

yes that is perfect!! So do i just pipe it on and random ways to get the effect?

Yup.