Sticks Like A Bur is an achievement in Metro 2033, awarded for killing a total of 15 enemies with sticky grenades. Also note that that achievement can be accomplished by killing either mutant or human enemies. The kills can be accumulated throughout one playthrough of the story and does not need to be completed in one play session. Multiple kills will also count towards the achievement providing that the sticky grenade sticks to an enemy first. An easy way to complete this is throwing the grenades at clusters of rats near the end of Ghosts. Another tactic is to sneak around enemies around fires and throw such a grenade on one of them. Using sticky grenades against demons, which is effective if done properly, will help you gaining this achievement; this will help in gaining the Inquisitor achievement as well.