As you know, engineers dont have that many recipes that are usefull to non-engineers, but we do have a few...
Mine include the following:
+10 damage scopes for ranged weapons except thrown naturally...
Mana Potion injector (20 mana potions in one bag slot instead of 4)
A wide selection of firearms, including the awesome Gyro-Stabilized Khorium Destroyer once i hit 375 engineering.
Ammunition for above firearms, Including 43 DPS Adamantite shells.
Landmines, Handgrenades and other explosives.
Cogspinner Goggles (random enchant leather goggles, cheap to make, excellent source of shards and dust when disenchanted)
Repair Bots for instances and raids, and various other automatons.
Questions, orders and whatnot is to be sent to Znayoo