How about the best individual performances as a 'domestique'? I've only been watching alot of racing for a couple of years, so my knowledge is limited, but here are a few:
- Axel Merckx faithfully towing a hopeless Landis on Stage 16 of the 2006 TdF after he bonked
- Andy Schleck at last year's LBL, going on the attack early and hard so that Valverde and Rebellin towed Frank back up to him... then getting dropped on the climb after caught, regaining composure, catching back up, and attacking again! Of course Frank couldn't make the counterattack stick, but it was an amazing piece of work.
- Kloeden staying with a dropped Vino on the first mountain stage of 2007 TdF, losing 2 minutes on a move that he could have followed (he's shown a spirit of sacrifice in last year's Giro and Vuelta too, and probably will in this years Tour)
- Chris Anker Sorensen dying a thousand deaths to get the Breschel group to catch Ballan at last year's worlds (didn't work, but holy crap was he spent)
Those are the first few that stick out in my head.