@ucme The Agera is properly fast, but the Koenigsegg One:1 is the new benchmark for absolute top speed. It’s yet to be clocked, but it’s a dead certainty to obliterate every production car record there is.
The answer to the question depends on the definition of “fastest” though. The One:1 is the fastest in a straight line, but the Porsche 918, McLaren P1, and Ferrari LaFerrari may beat it on a tight circuit depending on conditions. An honourable mention must also go to the BAC Mono. There’s footage on Youtube of a Mono keeping up with a P1. On a tighter circuit, it may have won. I’d take the LaFerrari on a mountain pass, but the One:1 across an open plain.