Many FBO's say a fuel purchase is required. However, a little flirting, complements on hair and shoes, pack of M&M's etc will get you and the other pilot a t-shirt without having to get the minimum fuel purchase. This is only a partial list for free t-shirts.
Preferred Jet Center- RYY
Million Air- SLC, TRM, HOU, MRY
Jetsource - CRQ
ACM- SJC
Jet Aviation- BED
Business Jet Center, DAL, OAK
Wine and/or Steaks (w/ fuel purchase)
Flower Aviation PUB, GCK, SLN (it's been a couple of years)
Wine only; (w/ fuel purchase)
Monterey Jet Center- MRY
Bridgeford Flying Services- APC
Free Breakfast;
Signature-BWI (Omelette bar on Wednesday mornings (stopped for holiday season, resuming in 2nd or 3rd week of January))
Free Hot Dogs;
Signature- MIA
Free Ice Cream-
Jet Aviation- PBI
Signature- MIA
Free Hot Mystery Meat Pies (not too bad).
Scottsdale Air Center- SDL
Back in the 90's when I was flying freight, some FBO at a small airport in the Carolina's gave you a 750ml bottle of liquor of your choice when you purchased fuel. I wish I could remember which one. Does anyone know of this place?