I'll break my answer into two categories.
The first category is those things that I keep saying I want to do, but we end up not making time in the schedule to actually do it. Such things include doing Disney Quest, going back to Winter Summerland Mini Golf course (we did that one once, in 2007), playing mini-golf at Pirates Cove at the crossroads, spend a little time in Innoventions. I could probably think of others to put in this category, but that's what I come up with for now. For this category, I'm not sure that I can say I "don't have the chance" to do it, because we do. The oppurtunity is there, we just choose not to do these activities, in favor of other things. So it's not that we don't get the chance to do these things, but they just get snuffed out with other stuff.
Now the second category of things would be stuff that *I* genuinely want to do, but I don't get the chance to do it because my other half isn't on board. I would love to go to one of the water parks someday, but my wife is terrified of water and my little boy is only 5. Next year, he will be almost 6, and it will be the first trip for our daughter who is turning 2 this month. So they're too little to go to a water park, my wife refuses to, and I have no desire to go all by myself and my wife would have a fit if I chose to do so and leave her watching both kids. I hope that when the kids get older, at least one of them will go to a water park with me, otherwise, I'm just never gonna get to do it.