Heh.. I was just looking for different applications of the CF trick when my mind went to the maridia tube. It's only 1 block high, right? If you glitched through that, would there be water on the other side?
..then I remembered that somewhere during the crystal flash, you're bound to drop a power bomb. Drat! :(
I found only one place besides GT, but this one will be difficult: gravity without phantoon and xray:
Things needed for this to work:
- The required rooms are all working without killing phantoon. They should be, but you never know.
- The door leads to the expected room. (The bridge you travel through appears to be a different room, because it has an extra enemy, so who knows?)
- You can somehow time a CF up there. Space Jump or wall jumps won't help since you can't re-spin after unmorphing, and there's no ground near you. If this is possible at all, it'll have to be done as part of a very tricky IBJ sequence.
Considering that this has been possible with xray for ages, I'm not sure it's worth it. Unless someone considers glitching through a 1-block floor to be less "glitchy" than xray-climbing behind a closed door.
Even if possible, it's useless in any% and low% (no grapple, not enough ammo) and 100% (need to kill phantoon and clear WS anyway). It might be useful in an RBO, if you relabel it as "reverse boss order except for phantoon who is totally skipped and we didn't feel like doing Kraid either because we don't need varia any more".
Meh.