Okay, it's been a few years since I've been to Universal so some of this may be outdated (example: if I start to tell you about Back to the Future, ignore me

)
Jimmy Neutron: you can take the
ECV in and park it off to the side, then transfer to a seat. If you want a moving - vs. stable - seat, be sure to tell the staffer.
Gruesome Gory (the special effects show): I think you can stay in the ECV
Terminator 2: 3D: stay in the ECV
Men in Black: regular line, eventually you get directed off to the elevators
Not Alf, the cute guy... ET: as far as I recall, stay in the ECV until you get to the attraction; may be some walking
Jaws: I remember being directed off to a different gate and there being some confusion, but I eventually got to ride. There's a higher seat in the back of some boats for guests who have trouble getting in and out of low vehicles (are you listening, Walt Disney World?

)
Earthquake: stay in the ECV until the subway, staffers will move it to the other side of the track.
Mummy: I didn't ride this in Florida; in California, I was directed through the exit.
Cat in the Hat: I once tried going through the regular line. Big mistake - and I'm good with the ECV, so it wasn't me

I was then sent in through the gift shop/exit
Drawing a blank, but the 'mystical' attraction: stay in the ECV the entire time.
Dueling Dragons: The one time I rode this I was the only person on that entire side of the park at the time - I went through the entire regular queue with no problem.
Live-action show: stay in the ECV
"Kid" coaster: take the ECV partway through the exit, then walk.
Jurassic Park: Stay in the ECV
Dudley Do-Right's Ripsaw Falls or Popeye & Bluto's Bilge-Rat Barges: I get these mixed up. I think they were only both open at the same time once, plus I only ride DDRRF rarely. It scares me

Okay, I know. I don't remember the Barges at all, but think it would be similar to Kali River Rapids. For Dudley Do-Right, I get sent through the exit. This attraction has a log with a seat that can be raised for, again, guests who have trouble getting in and out of low vehicles (are you listening, Disney?

).
The place I have the most trouble - hassle - is in Marvel Super Hero Land. I keep getting told I can't take the ECV into the attraction, that I need to transfer. I'm polite but firm. I can't maneuver myself - well, I can, but not well AT ALL on inclines. Plus, at least at Dr. Doom's Fear Fall and Incredible Hulk, there are elevators. At Spiderman I've gone in through the exit, and at the similar-to-the-teacups attraction, I think there's one vehicle with a double 'door' and a ramp?