All of the motors that many of you mentioned are very good motors. The OS 12tz has a stupid low end power band that will shoot you out of corners like a rocket. The RB V12 is an all-around workhorse with a good balance of low-end and top-end (much like the MT 12). The Picco Mega motors can be ballistic, but you have to have an associates degree to find that tuning balance. But, lets not forget about these motors (even though three have been recently discontinued):

Novarossi NS3 (discontinued)
Mugen X12 (discontinued)
Pixi Black (discontinued)
Max Power 12s3 (the RB v12 on roids)
Rex RER (Nova's Pixi Black)
Nova RR12 (and its cousins including the Rex)
Sirio Evo2 and Evo3 (makes some stupid power under the radar)

You pretty much cannot go wrong with any of these motors. They all have plenty of usable power with some to spare. Most of the above are $250 and under except the Max Power and Mugen X12 motors. So, there you have it. A good range of motors that will fit in whatever niche you have.