Pacquiao active. Ali, Frasier, Foreman all time (and I would count all there because they sort of were the perfect men to fight each other at the time) I guess the Gatti/Ward trilogy would be up there as well.
Frazier, PAC, Tyson 
check this out gage if u havent seen before
Have I seen it??? I own the mutha fuckin DVD son! Sits right next to the smashing machine!
Smokin Joe
gage949 - Have I seen it??? I own the mutha fuckin DVD son! Sits right next to the smashing machine!
haha I own it too. Good shit man.
My buddy Zac Wohlman of course! Just won his pro debut this past Thursday. I guess that's what training with Freddie Roach for the last 4 years will do for a guy.
http://youtu.be/EqJia6Tc2do
Joe Frazier
Gatti RIP! Came to brawl and fought with everything he had. Partied hard and lived a fast life. I miss him in the ring... Still believe the wife did it!
Of all time: Sweet Pea, Prince Naseem
Currently: Pacman, Ward, Donaire
Pacquiao now,Max Baer and" the mountain" Primo Carnera,still have my hair stood on end every time i watch them!!
of all time, Marvin Hagler
Current king kahn & $ mayweather 
Carl Froch
Tua
Andy Murray , Eric morales , Marco Antonio barrera!
Marcos "Chino' Maidana , he is very raw powerful puncher. Took a liver shot and got up, BALLS!! Very exciting to watch and he is very sneaky ,,, lets you think you are winning and then BOOM you are looking at the lights
My favorite boxer is Tiny Mexico. Julio Cesaer Chavez was a true gift to the sport and that body attack was so sweet to watch. I used to flip flop on Morales and Barrera as to who I liked as my favorite fighter throughout their respective careers.........then I had a major fancrush on both Rafael Marquez and Israel Vasquez during their trilogy which carried over to whomever they fought. When two guys give their all the way these little Mexicans do during these ridiculous trilogies........even though there is often some deep seeded animosity between them, how do you as a boxing fan not come away loving them both equally for the gifts they have given you as a fan. However, my very favorite to watch over the past four or five years has been Juan Manual Marquez, and the most recent fight with Manny was something so beautiful to watch that I'm still wearing the goose bumps. It is too bad he is oone of the biggest hard luck stories in the sport with regards to the decisions in this particular trilogy with Manny, but it takes nothing away from what we all witnessed on those nights, and I give Manny all the respect in the world.......it is a judged sport and never the fighters fault when things turn out the way they do.
Lets not forget Jose Luis Castillo and the way he effectively applied his mentors style to the craft himself with a Chavez like attack to the body.........and that fight, oh you all know the one.........that fight with Corrales which comes immediately to mind when people ask about the greatest fights you've ever seen. I also like to keep Corrales on the perimeter of this group just for sounding Mexican and having such an exhilarating style. Lastly, while Alvarez does not have the agro aggressiveness of the typical Mexican fighter and still has much to prove, he is something special on the horizon and I will watch him closely and hope that he can find his nemises that will bring out the best in him and allow him to possibly leave his mark on the sport with another spectacular trilogy as so many of his predecessors have.
So my answer is all these stubborn little badasses from Mexico are my favorite fighters!
Of all time: Hagler
Currently: Sergio Martinez
Currently: Pac, Ward, Mayweather.
All-time: Tyson, Ali, RJJ, Jack Johnson