2. The Russian 2-on-1
When it comes to being offensive against larger opponents, after the snatch single, the technique I point my students to is almost always the Russian 2-on-1.
When dealing with size disparities it becomes imperative to focus on putting yourself in a position where you can maximize leverage. Developed by the Soviets in the 80s, the 2-on-1 is a hand-fighting (or "grip-fighting") based takedown technique which creates a dynamic where both of your arms work in unison to isolate and attack just one of your opponents arms (from a Jiu Jitsu perspective, one could think of it as the takedown version of the arm bar).
Just like the snatch single, the magic of the 2-on-1 relies on isolating an opponents appendage. Unlike the snatch single, the 2-on-1 is best designed for grappling scenarios. It definitely is fit for certain self defense scenarios; we actually have policemen at our gym who are trained to use the 2-on-1 to control civil disputes which turn physical, but in general it's best suited for sport grappling situations.
You be the judge. Study the attached video and decide for yourself if you think this wrestling-based takedown set up has a place on the street or strictly the mat.
PS - my personal opinion is your skill level with the 2-on-1 determines if it's a viable option for self-defense. If you're hitting it on large partners on the mat consistently then you can probably rely on it off the mats too.