So people gush over bmim and get the guaranteed publications for including "ionic liquid" in the title of their article. Ionic liquids are far from the newest fad, though, they've been around for nearly 100 years!
93 years ago, Paul Walden reported that ethylammonium nitrate actually melts just north of room temperature. Ionic liquids are hot now, but did you know they were about a century old?
I don't know if you want to go heating this stuff too far above RT! :-)
1 mol sulfuric acid + 1 mol water = 2 mol liquid hydronium bisulfate. World's oldest ionic liquid?