Magnesium ribbon. 
Magnesium ribbon can be lit with a match and it will then burn brilliantly and slowly along like a slow-motion fuse.  It's really a very gentle, calm thing to see, though it will blind you if you look too long.  Burning magnesium ribbon is a standard high school chemistry lab demonstration, to show that metals can burn.  Iron burns too (you can light fine steel wool with a match), but magnesium burns a lot brighter. 
Surprisingly, it's a little bit hard to buy magnesium ribbon: Standard lab supply companies won't sell it to private individuals.  But other companies will (see the Source link). 
Source: United Nuclear 
Contributor: United Nuclear 
Acquired: 11 April, 2003 
Price: $7/roll 
Size: 3" 
Purity: >99%
 |  
  |  
 |  
  |