League of Legends (LoL) Question: Who is the best jungler qua go-around?

Here are some ideas, in a rough decending order of what it sounds like you might like.

Kha'Zix sounds like one of the closer champions to what you're describing. He clears pretty quickly and safely, has great mobility, and excellent assassination potential.
Shaco sounds like the closest champion to what you're describing. Takes a bit to get the hang of jungling him safely on first clear, but clears very well after that, and is definitely an 'ambush' champion.
Vi is a pretty solid suggestion. Very burst focused, and there aren't a lot of champions that can fight her straight up. Her jungle isn't the fastest, but it's not bad, with the right runes.
Jarvan IV doesn't clear the fastest, but has quite a bit of mobility and engage, and can do a lot of damage, if you decide to build him with it.
Lee Sin is a classic, but takes a lot of practice. High mobility, high sustain, strong 1v1, but have to play around getting picks. Very mechanically demanding.
Wukong is low sustain, but clears fairly quickly, and can make some good ambush plays. Might be worth looking into.
Shyvana has fallen out of the meta, and I honestly don't know how she does right now, but might be worth looking into.
Rengar is a strong assassin/fighter pick. Lots of mobility, fast clear speeds. Kinda needs to snowball to win though, and demands a good understanding of positioning and timing.
Nocturne doesn't have a lot of control in jungle right now, but clears quickly, stays healthy, and can get around the map quickly. He's really good for engaging on a single split target from a distance, and can be built with quite a bit of damage.
Elise doesn't sound exactly like what you're after, but might be worth looking into.
Evelynn takes a while to get the hang of, and her early jungle is a bit dangerous, but she's definitely an 'ambush' heavy jungler.
Hecarim can be played with more damage, but he's generally build on the tankier side. Still, maybe worth looking into.
Nidalee might be worth looking into. Very control heavy, kinda like Elise, and pretty mechanically demanding.
Kindred clears well, but takes some practice to get the hang of, and works best as a control jungler.
Graves works well as a carry jungler, if you'd rather focus on playing selfish and farming up.

As a Shaco main, I would recommend him because he is great mobility and ambush potential. My strongest build includes buying Boots of Mobility so you have great map coverage. Also, Shaco's Q helps him to gap-close and gank without the enemies seeing him.

Some other champs I recommend for you include Kindred, Elise, Evelynn, Graves, (AD) J4, Nocturne, Skarner and (AD) Wukong. They suit your criteria well and can be very effective in the jungle.

Kha'Zix would be of the less tanky and more ambush variety. You can also play Vi more like an assassin than she is typically built. For me, Vi's virtually guaranteed lockdown is a replacement for Warwick against many highly mobile champions.

I dont readed the comments, but atm Graves/Lee/Kha//Elise is the way to go :)