Lets see here...
Austria - Hochschaubahn
England - Nemesis
Canada* - Leviathan
Germany - Winjas (sorry)
Hungary - Hullámvasút
Netherlands - Troy
Norway - Thundercoaster
Spain - Dragon Khan
Sweden - Lisebergbanan
United States - Boulder Dash
Wales - Speed
(Czech Republic, Ireland, Switzerland all coasterless for me)
Canada pt2.
ON: Leviathan
QB: Goliath
And since people are doing it by US states as well...... I guess I'll waste time on my day off for this.
Alabama - Cannonball Run, Waterville USA
Arizona - Didn't ride a coaster
Arkansas - X Coaster, Magic Springs & Crystal Falls
California - Tatsu, Six Flags Magic Mountain
Colorado - Didn't ride a coaster
Connecticut - Boulder Dash, Lake Compounce (and my #1 US ride)
Delaware - Didn't ride a coaster
Florida - Kumba, Busch Gardens Tampa
Georgia - Goliath, Six Flags Over Georgia
Illinois - Raging Bull, Six Flags Great America
Indiana - Lost Coaster of Superstition Mountain, Indiana Beach
Iowa - Legend, Arnolds Park
Kansas - Roller Coaster, Kiddieland (IDK, both coasters I've ridden in Kansas were kiddies...)
Kentucky - Kentucky Rumbler, Beech Bend
Louisiana - Gilbeau's Galaxi, Dixie Landin' Family Theme Park
Maine - Excalibur, Funtown Splashtown U.S.A.
Maryland - Wild One, Six Flags America
Massachusetts - Superman ride of Steel, Six Flags New England (IE: NOT Bizarro)
Michigan - Shivering Timbers, Michigan's Adventure
Minnesota - Wild Thing, Valleyfair!
Mississippi - Didn't ride a coaster
Missouri - Outlaw Run, Silver Dollar City
Nebraska - Big Ohhhh!, Fun Plex
Nevada - Manhattan Express, New York, New York Hotel & Casino
New Hampshire - Yankee Cannonball, Canobie Lake Park
New Jersey - El Toro, Six Flags Great Adventure
New York - Comet, Great Escape / Silver Comet, Martins Fantasy Island
North Carolina - Afterburn, Carowinds (although its on the SC side... so if I have to pick something in NC, I guess...Hurler)
Ohio - Diamondback, Kings Island
Oklahoma - Wildcat, Frontier City
Pennsylvania - Cyclone, Williams Grove or Storm Runner, Hersheypark
Rhode Island - Didn't ride a coaster
South Carolina - Hurricane, Myrtle Beach Pavilion
South Dakota - Didn't ride a coaster
Tennessee - Zippin Pippin, Libertyland
Texas - Superman Krypton Coaster, Six Flags Fiesta Texas
Vermont - Didn't ride a coaster
Virginia - Apollo's Chariot, Busch Gardens Williamsburg
West Virginia - Big Dipper, Camden Park
Wisconsin - Avalanche, Timber Falls Adventure Park
Ehh, just to toss it out there....
Haiti, Jamaica, and Mexico have been visited but no coasters ridden. Although I did ride the AlpineCoaster in Haiti, Dragons Tail.