what grappling style goes good with shotokan karate? I would like to become more rounded by learning some grappling arts like jui jitsu or judo or something like those? does anybody have some suggestions?

I would think any of them would complement any style well enough. Choose whatever is local and has the best instructor.

Good luck.

Any grappling style would go well to help your groundfighting skills. Just take a look around your area to see what is offered.

The honest answer - None really. Shotokan style posture and stance do not translate at all into grappling, it's like giving a single leg takedown as a Christmas Present.

But anyhing with a lot of sparring is good. Judo, wrestling, BJJ, Submission grappling, sambo, catch...

my sensei trained for a couple of years in judo and he sometimes teaches us judo techniques a treat when everyone is working hard. i think judo or aikido would go pretty good because jiu-jitsu has kicking techniques and punches where as judo and aikido have almost none.

Everyone is correct. Any of them are going to mesh well. It's up to you to work hard to combine them into a system that works for you. I'm partial to BJJ and Diato Ryu Aiki Jujitsu. But I'm biased in that regard.

BJJ is probably THE best base atm...