The nicest savoury snack I've had on SNBA is this one:
Which was a chicken salad sandwich served on flight SN2047 (BRU-BHX) on 3rd November 2004. This was on our old "friend" OO-DJG (of the used sick bag aroma).
The nicest sweet snack on SNBA:

The cherry tart served on SN2177 on 17th November 2005. Also on board OO-DJG.
Other nice meals have been:
On VLM a nice crusty roll with cheese, a pain au chocolat on one flight and a chicken sandwich accompanied by fresh fruit salad on the return.
On Air New Zealand nice breakfasts consisting of scrambled egg, sausage and strawberry yoghurt and a nice meal of a Thai-style meatball with water chestnuts and rice.
On Icelandair we had breakfast similar to on Air New Zealand.
On British Airways VC10 tells me she had smoked salmon and fillet steak, which was good.