Depends upon my mood, the music to be played, the volume required, and the acoustic environment. On the tube amp side I would have to say the Sadowsky SA200 stands out as the most versatile tone monster although a bit limited on extreme volume. Ampeg SVT, Trace Elliot V8, or perhaps a Reeves Custom 400 if more volume is required. The V8 has a nice stringy quality in the mids and can get narly while the Reeves is a bright clean machine with tight, deep lows. The SA200 can cover most of the tonal range of the V8 and Reeves and creates it's own unique and highly desirable dirt, but IMHO doesn't really cop the grind and grunt of a cranked SVT. Ashdown 427 is possibly the hugest sounding and heaviest tube amp I have ever played, another clean machine but a bit pillowy. If you want to feel like you are in an arena on every gig, the 427 is the way to go. At the other end of the power spectrum, a Fender Showman sounds awesome for bass.
On the hybrid side, hard to argue against a Genz GBE 1200 for versatility, power, and tone, but there are times when I would prefer an Ampeg 8 Pro or Mesa Titan. The 8 Pro can sound very close to an SVT but covers a bit more tonal ground and gets much louder. The Titan is perfect anytime you want maximum presence in order to dominate the mix. It causes the entire building to shake even at low volume.
On the solid state side, GK RB series amps can be super punchy or scooped. Great for an aggressive rock sound or slap. I even used one in country band and loved it. If you want a more woody tone, Epifani 902C has you covered.
There are several other amps I have played that would be better for one thing or another...you get the idea. There are also several amps I would love to play, but that will have to wait until someone makes a donation or I win the lottery.
