I use the 266 to line my eyes with shadow, not sure if this would be "smudgey" enough for you though. It tends to get a pretty defined line, but you could always smudge it out afterwards, I suppose.
For MAC brushes, I (as well as everyone else, it looks like!) like the #219, and the reaaalllly small brushes like the #228 and #231 are also great...
For other companies, NARS has a WONDERFUL smudger brush that just blows the others out of the water when it comes to smudging and under-eye work! It's a little bit expensive (but really no more so than MAC), but it sure is worth it
Funnily enough, I have about a gazillion brushes - MAC, Chanel, Shu, UD, TM... but for smudging I like to go over my applied e/l with a $1 sponge tip E.L.F. smudger brush: http://www.eyeslipsface.com/products.asp?dept_id=1025