Most notable ride type / category you HAVEN'T ridden?

[davidm]

Steeplechase is two rails though, just oriented vertically.

(in all seriousness, it does have running wheels on each of the "rails")

 

[Coaster Hipster]

Morgan Hyper (though I rode Santa Monica Pier coaster...)
Arrow Wild Mouse
B&M Launch
RMC Raptor
Any Togo model

 

[criticalboot256]

i think it'd be easier to list the models i have been on, but i do really want to go on a dive coaster at some point, but also any type of wooden coaster is definitley up there too

 

[Railfan uk]

This one is easy for me I have never ridden an RMC