I saw Flashback on two occasions ; 2002 on my first ever visit to SFMM, when it was allegedly still running (but it was July, so it seems they didn't run it in the summer and I knew no better anyway as I was at my first ever BIG park and just awestruck by the amount of coasters there), I went back in 2006, knowing a bit more, but it was SBNO then.For rides that are gone.. I always wished I could have ridden Flashback at Magic Mountain. Mainly to see if it really was as bad as people made it seem.. and because it looked like it *could* have been a fun ride. Would love to see B&M make a modern version of it. haha. Maybe also Viper at Great Adventure, again just to see if it was truly as bad as people said. I saw it closed, never got to ride it.
I did ride Viper though, in 2003 ; it was not good.
The ones that had intrigued me for a while were Olympia Looping (but got that when it first visited London as I'm too basic to have got it elsewhere) and also Dragon Mountain in Canada, got there this summer and really liked it (but again, it is not objectively good at all).
Nowadays? Maybe those Chinese bullet coaster things (although I have done an air-launch or two), certainly not those Maurer spike things though (despite the people at work sending me links to that one on the cruise-ship as if I'd not heard of it). Maybe those ridiculously long one-way alpine coasters they have in the mountains in Europe ; that's gotta be done some time (but they are not really a coaster are they?)