How do you make a great cut in glass easily without a glass cutter?

Why don’t you want to use a glass cutter? That is the only thing I can think of to cut glass with.

Why do you not want to use a glass cutter? That is the only tool that will get the perfect cut you are looking for.

You can find one for 5–6$ at your local hardware store or on amazon.com.

Good luck!

Could one use the edge of a emerald-cut diamond, should one have an emerald-cut diamond laying about?

You can cut a wine bottle with string and nail polish remover.

@augustlan: Jeez. “Put on your goggles; find a fire-proof surface; ignite the string.”

Maybe try carving into the surface with a knife or other sharp object, and then give it a good whack. I should fracture at the weak point, the carved groove.

A hillbilly chainsaw. It’s basicly a steel wire with burrs on it that’s attatched to two rings. A.T. thru hikers use them to fell trees for firewood if their fuel runs out.

The BEST tool I can think of is a high-pressure water cutter but few of us have access to one of those (maybe @jerv or @LuckyGuy do…).
If you’re determined to not use a regular glass cutter, I think @Mr_Paradox‘s suggestion of the cutting wire might be the best suggestion above.