On to the level 35-49 range! (level 225-300 engineering)
Even more powerful bombs are available, though I only list the ones I usually use, since the others are to costly for my tastes. Dense Dynamite at level 250, and Fel Iron Bomb at 300. I never actually make Fel Iron bombs at this level though, since I hate not getting skill points. I usually just shuffle them from my level 50+ toons, since they make them to advance their engineering at that level.
Not much in the goggle department in this range, since you'll have started to get stats on your helm drops by now.
More class borrowing though.
Resurrection - Goblin Jumper Cables XL have a much higher chance of working. /yell "Live, dammit!" when you're gonna shock someone.
Underwater Breathing - Don't have a shaman/warlock with you? Don't feel like stocking breathing potions from an alchemist? Just pop on your Deepdive Helmet when you're running low on air, then switch back.
More Attack Pets - The chicken, walking bomb, and two dragonlings become available in this range, though you'll have to be level 40 and 50 for the dragonlings, goblin engineer for the bomb, and a gnomish engineer for the chicken. Also, unlike before, they've been severely nerfed. They used to scale in level with your engineering level, meaning that you could have a guardian pet that was a lot higher in level then you were. Plus, if you are a dedicated engineer, at level 50 you'll be crafting Burning Crusade trinkets, making the Arcanite Dragonling unnecessary.
Mind Control - Mind Control, not just for priests! Tricky to use though, the one time I tried it I couldn't get out of combat, and kept getting swarmed by mobs.
Death Ray - The signature attack of the new Cataclysm hero class, the Combat Engineer! Seriously though, if you use this during the 35-49 range, it will help a lot. You really need to couple it with the bubble belt/paladin bubble/Mana shield/Void Walker Sacrifice/Power Word: Shield to get the most use out of it though, since it will hurt you severely while charging otherwise. This is one of the reasons that all of my engineers go Gnomish except paladins, and even they go gnomish first to get this and the chicken, then go Goblin after. And this was when you had to drop engineering to switch specializations too. And go uphill to school, in the snow, both ways......
Self Portals - Before the portal in Dalaran was available to drop you in front of the Caverns of Time, you had a long flight from TB or Org to get to Tanaris, and an even longer one from Darnassus. The Gnomish Gadgetzan teleporter and the Goblin Everlook Ripper give level 260 engineers a time saving device that they can use every 4 hours. Just remember, keep fire extinguishers and healing spells handy when going to Winterspring, and keep your parachute on when going to Tanaris. Accidents can and will happen. Also, be prepared to /yell "You no take candle!!!" when tranformed into a kobold in the teleport chamber.
Other fun gadgets - High Powered Flashlight, Goblin Rocket Helmet, and the Gnomish World Enlarger.