Never been a star-struck type (interviewed many a music and sports star/legend for TV), but a few have got me tongue tied when I first met 'em- Todd Rundgren, David Bowie, U2, Gary Payton, B.B. King.
No easy feat, since in my line of work, I've met, interviewed or ran sound for anyone from Avril Lavigne to Yes...
blues, rock, country, jazz, sports...
very fortunate, and not jaded!