[quote name='crunchb3rry']Saccharin is usually what makes them taste like shit. That "sugar free bubblegbum" aftertaste.[/quote] There are no major-brand sodas made with Saccharin. Nearly all are Aspartame (Nutra-Sweet), though a few (Diet RC, Diet Rite, certain versions of Diet Coke) are made with the far-superior Splenda.
I use Splenda at home almost exclusively. For coffee, iced tea, etc. My wife even bakes with it 90% of the time. Tastes great.
As for diet sodas, the Aspartame-sweetened ones with the least offensive taste IMO are Diet Coke/Pepsi with Lime, Dr. Pepper (especially vanilla), and Mountain Dew Code Red (actually better than regular IMO, same taste, no gross syrupy stickyness).
But every year around passover I head to a grocery store in one of the Jewish neighborhoods and score some Kosher Coke. Mmmmmm 100% pure cane sugar goodness. Last year Meijer even stocked 2-liters of Kosher Pepsi. We got some, but it doesn't match up to the Coke. Goose Island Rootbeer is also made with cane sugar, and is

ing awesome for those who can get it (I live in chicago, so I'm golden

).