What Is Twinking?
From GnomiesWiki
Simply put, twinking is making the best character you can for a particular purpose. This means the twink character will have the best gear and enchantments obtainable for their level. Usually that purpose is to engage in PVP or Player Vs. Player combat, either in designated Battlegrounds (BG's) or arenas. It is mostly for PVP in the Battlegrounds. Since the Battlegrounds (Warsong Gulch [WSG], Arathi Basin [AB], Alterac Valley [AV] have certain level brackets, people will select which bracket they will create a twink in. Some brackets are: levels 10-19, 20-29, 30-39, etc. The 10-19 bracket is the most popular for twinking since gear is relatively easy and inexpensive to obtain for a level 19 character. Obviously you would want to be at the highest level you can in your particular bracket, so most twinks end up being a level 19 twink, or a level 29 twink, etc. This is due to the fact that you max out your attributes for that particular bracket as well as talent points.
Most people who twink will create a twink on the same server where they have a main or at least generous friends. Twinks are a tremendous investment of time and money, especially if you get really serious into it with high level enchants for your gear. This is where your main and network of friends come in. The main can gather mats for these expensive enchants and/or farm for specific pieces of equipment to complete your twink. Sometimes you'll even want to obtain several sets with different enchants for specific situations. Your main can also just farm gold to buy the necessary equipment and enchants. Other ways to use your main include crafting specific gear (e.g. Deviate Scale Belt) or consumables (e.g. Swiftness Potions or Sharpening Stones) that will be used quite liberally in the BG's.
Some people look down on twinking as ruining the fun for the casual players or even go to the extreme of thinking that it's a form of cheating. To me it's simply trying to be the best you can be. Twinking in my view is actually quite a level playing field since everyone has access to the same gear and enchantments, especially for the lower bracket twinks, like a level 19 twink. When you get to a level 49 twink for example, it may not be obtainable for some because as you go up in level, the good gear gets progressively more difficult to farm for. Besides, there's nothing better than to totally and completely pwn another player, especially a twink. And that's why <Rolling With My Gnomies> was formed -- to be the best twink guild (level 19) that we can be. I think that we've achieved that on our home server of Stormscale and even within our battle group. If you ever see a full (or even half full) group of gnomies in WSG, you better watch out!

