The best advice was mentioned earlier - ask your classmates about which rotations are particularly good. The 'ideal EM rotation plan' is squat if the teaching is poor or if you are stuck behind fellows and residents to learn.
That being said, here's my advice on rotations:
I agree that anesthesia is great. My residency (and I assume most others) have a dedicated anesthesia block where your sole responsibility is to intubate. I worked with anesthesia attendings and often they asked how many tubes I had done before they handed me the blade. Since I had some under my belt as a student, this really helped facilitate my experience.
I did a derm rotation and found it to be helpful. That being said, there's very few derm emergencies and they usually are pretty obvious.
My residency doesn't have an ortho rotation and I think more experience with that field would be helpful. Be careful not to wind up spending too much time in the OR or on post-op rounds b/c that won't help you.
Ophtho could be a big plus. If you get some structured learning with the slit lamp that would be a bonus. On my community ED rotations, I see eye complaints just about every shift and I still feel it is one of my weaker areas.
Not so sure about cards. I read ECGs every shift in the ED and after my ward month as an intern (at the VA with tons of rules outs, CHF exacerbations, etc) - I feel very comfortable managing basic cardiology in the ED and knowing their path as an inpatient. Also, learning the gazillion stress tests and indications for them probably isn't super high yield since that's an inpatient work up (and also very institution dependent).
I feel a ICU rotation would be more useful (particularly if your med school didn't require one). One of our intern year ICU rotations has a ton of autonomy and I was very happy to have some ICU experience as a student before walking into a 30 hour call by myself.
Rads - a vacation rotation at my med school. I'm not sure if anyone got much education but it was a great time for step 2 or interviews.
Trauma - you'll get plenty experience during residency. I would wait on this. Plus, unless you are somewhere absolutely insanely busy or without any residents, you probably won't get any procedures.
Tox - My residency has a dedicated month for this so I don't think I needed extra time. However, if we didn't have this month I would have liked more time.
ID - Probably low yield. My experience with inpatient ID is that you had something that crazy come through the ED, ID will be consulted as an inpatient and the ED will be giving broad spectrum abx anyway. My personal thought is just to consult your PDA or EMRA abx guide and call it good. I can never remember what covers what (even though medicine folks love this topic)
Good luck!