My teenage nephew has just started taking lessons on the electric guitar. I am thinking about getting an effects pedal ("stomp box") for one of his Christmas gifts. I used to have multi-effects rack unit for my keyboards (before I started getting involved with computers and sampling). It cost a fortune and had every effect under the sun (chorus, flanger, reverb, etc.). I gave it to my niece when she got her first electric guitar, so I am sort of starting from scratch with my nephew and basically wondering what professional guitarists would consider the most useful effect for a novice player.
If this helps, he is typically playing solo or with one other guitarist (a friend, who -- although she is not much older than him -- has been studying for years and is all ready giving lessons at a music store.) I can only remember the names of two groups that he said he likes Yellow Card and Blink (something or other). I have no idea what they sound like. But, I imagine at some point he will be interested in playing their songs and if there is an effect pedal that they use a lot, I think he would appreciate that one the most.