Tran'rek is a level 45 quest giver located in Gadgetzan in the contested territory of Tanaris. His name is a play on the term "train wreck", which is appropriate for a goblin.
Krazek is his cousin.
He starts the following quests:
[45] Scarab Shells (Dungeon)- [50] Thistleshrub Valley
- [54] Super Sticky
See List of Tanaris NPCs.