I think some may take it more serious than I meant it!
We just were at the mall with our ten month old son an let him ride it. Once he was on, we discussed if this counts as his first (powered) coaster or not. And soon we had the point, up from which elevation change, up from which size an up from which speed it could be truly called a coaster, because the design of a locomotive with wagons on rails is found on many coasters and especially on powered ones (Mack's Enzians).
And soon after, we thought who would knew better than this community!
I think I'll go with Andrew and increase Paul's count to four!
Beast|Mystic Timbers|Wodan|Twister|Phoenix; Dive:
Flug der Dämonen|GateKeeper; Launch:
Top Thrill Dragster|Karacho; Floorless:
Flying Turns; <200ft:
Expedition GeForce|Maverick; >200ft:
Magnum XL-200; >300ft:
Millennium Force; Mine:
Colorado Adventure; Boomerang:
Steel Vengeance|FLY|Formula Rossa|Blue Gemini|Colossos|Kennywood|Hersheypark