Here are my nominees:
Obviously, the Mark IV. This is the amp that the phrase, "All the bells and whistles..." was designed for!
The Mark III, in 112 EVM, reverb, Simul-Class form, along with a 112 Theile. Read the manual and just set it to the sweet spots. Pickup a Strat, Tele, LP or 335 and just play your *** off. Don't worry if it sounds good--if you can play, it will. Simpler than the Mark IV.
Need simpler? The Mark IIC+. The holiest of all the holies. Trust me, it will have have you shouting, "HOLY COW!" in no time. (Or more likely, "HOLY $#%& !!!!")
The Dual Calibres: DC-2, DC-3, DC-5 and DC-10. I think the DC-3, and the DC-5 are probably the most usable for most people. There's not much you can't do with these amps. And like the rest of the 100-watt 212 combos that followed the DC-10--these are snarling, powerful beasts that can level entire city blocks! EAR PROTECTION, if you know what's good for you!
The Heartbreaker 212 is what a modern Twin should be. WAAY too much amp for most garage band semi-pros to appreciate--this amp is LETHAL, if not used properly. Really glorious though, when cranked.
The Trem-O-Verb. Still one of Mesas most popular amps. Remember the "Guitar Player" review? Something about, "...the Trem-O-Verb captures 90% of the vibe of the great Fenders, Marshalls AND Vox amps..."
When a great player like Kevin Eubanks of 'The Tonight Show" plays an amp like the Blue Angel, you have to figure there is a reason. You want clean? You want luscious? You want small amp Class A goodness and can't decide between 6V6 and EL84s? Look no further.
Finally, the Lone Star--take your pick. Do you need the headroom of the Classic 6L6 version; or the Special chime of EL84s? I think the book is still out on these; though enough people have raved about the great clean tones, the improved reverb and the amazing flexibility to make them "instant" classics. Any player looking for a new, modern amp needs to play these.
And while I love my Maverick 212s, this amp won't make this list--it's not a "metal" amp. It does get kind of a Plexi Marshall tone--so who knows what the right pedal could do?
And the Rectos will never be known for their clean tones--but did I ever tell you about the time I sat down with a Dual Rectifier and a Deluxe Reverb--and got the Recto to sound like the Deluxe? Only, it kinda sounded like a 500-pound Deluxe!
So, these are some of my favorites--what's yours?
Bill