I don't know about all of you, but Goldrush seems to be riddled with little spots that nobody seems to check, look at, or paths to defend.
EDIT: Video has been made. Is somewhat crude and is missing some spots (Such as the lamppost above stage 1 second point choke, and the rafters above stage 1 spawn), but hey - that's what you get for about 1 1/2 hours of jumping around and 20 minutes of actual work.
http://www.youtube.com/watch?v=ZRMczLicp8YOh, and as for the music - I know a lot of people hate this sort of stuff, but it's the visuals that count.
Stage 1
-Fairly well known by now, but the left-hand side of point 2 courtyard can be jumped by any class. There are two sewer pipes that stick out along the left wall. You can jump onto the second one, back up a bit, and jump onto the platform. This isn't too useful for anything but Pyro, Spies, and possibly Engineers. If you want to get up there as heavy, you have to jump from the first sewer pipe to the second. There is a corner involved though, so it will take some practice, but it's definitely possible.
-Basically the above method but in reverse. You can jump from the platform to the second sewer pipe (Defensive view) to the first pipe. This doesn't have much use except for spies who have fond remembrances of KZ Counter Strike maps, as it cuts down time to get to spawn-areas significantly.
-Again, fairly well known, but right above the sewer pipes there's a circular platform. You can get up there as an engineer by jumping with a dispenser or a sentry along the 100ammo pack and the small heal vial. Build a teleporter exit up there, and go to town.
-Less known than the rest, but above the stairway leading to the platform (the one that opens for offense to make an easier path to attic) there's a window sill. As defense, before the gates open you can sticky-jump or rocket jump up there as a soldier or demoman. I personally suggest demoman, just because it's easier to defend yourself due to your position.
-When the mine-cart is approaching the final checkpoint, you can jump on top of the cart (crouch-jump on the nose of the payload), and jump onto the platform to the attic, giving you a huge advantage to clear out that area.
-Near the stoplight right near the first point, you can dispenser-jump or sentry-jump high enough onto the raised platform to place a teleporter exit. Recommended spot if your offense sucks at covering their flank and you need a good, secure spot to build a teleporter exit.
-Aside from that, obvious dispenser-jump teleporter exit spots. Basically, if you see a platform, you can dispenser-jump/teleporter there.
Stage 2
-There really aren't a whole lot of spots in this stage of my memory. One, is right before the first capture point there's a canyon with a bridge going across. As anything that isn't a heavy or soldier, you can jump across the canyon by crouch-jumping along the righthand side with the right timing. If you miss you waste more time than you'd gain, but with practice you can easily get a 95% success rate. Good spot during the initial offense to circle-strafe sentries as pyro, or to sap as spy.
-When the payload is nearing the final point, you can jump on top of the payload and on to the bridge. Very limited use, but it has some. I guess.
Stage 3
-As defense when everyone is camping by the door, right below that raised doorway that people love to camp in the corner, there's a wooden frame right below it. By jumping and crouching, you can get into that little area and scooch towards the payload. Has much more use than most people think. People usually check the corner right below them for spies or pyros, but nobody ever checks the wooden framing to the left of them. Extremely useful for uber-ready medics, pyros, spies, demos, and in some cases heavies.
-After the first cap, if there are still defensive players waiting in the pathway that closes (You can tell because the door won't close), you can jump from the stairwell into the hallway as any class but heavy. If you want, you can jump on top of the payload into there as anything as well (including heavy), but this leaves you much more open as it takes a try or two to get on top of the payload.
-Right behind the 2nd payload point there's a platform section that engineers love to build sentries on. As any class, you can go to the platform right next to it (they're seperated by a wall), and edge along the building framing to get right up next to the sentry.
-The most useful (IMO) of all the ones listed. At the contested area between the final point courtyard and the long payload hallway, you can surprise the hell out of your enemy by going to the encoved area (the one with the 200 ammo box in it and right above the mineshaft goign to the bottom). Jump on top of the boxes on the right-hand side of where it starts to become a hallway as defense, and jump onto the wooden framing (seeing a pattern?). Go along the framing, jump aroudn the windowsill, and approach the corner. Face slightly to the left (if 0degrees is facing right towards the wall, I'd say -3degrees), and hold W while jumping forward. It'll take some practice, but you can jump onto the window framing right outside the enclosed area, and waltz right in. This loses it's use when sentries start getting built, but it surprises everyone.
-Similar to the other one, you can get into the area directly opposite the rafters i mentioned in the above tip. Jump onto the boxes, but this time on the left-hand side of the hallway, and get on top of the wooden framing. Edge along until you get to the 2 windows. These windows have weird detection, so you'll have to jump around them. When you get towards the edge and you can see the platform, run forward, jump, and turn your mouse and hold W and A and you should land on the platform. This one's use is limited, just because of it's difficulty and frustration, but if you can master it it's extremely useful as pyro/spy/heavy.
These are all the ones i know of. =3 enjoy