Grappling Hook
The diamond in the recipe is actually an RE-Battery, but I couldn't find the battery in the available smileys. The empty cell is for pneumatic pressure to propel the hook, and the mining pipe makes a great barrel. 
What it does:
The grappling hook fires out a line that attaches to the first solid block face that it hits. Unlike the grappling hook mod already available on the Minecraft forums, the IC2 grappling hook attaches to the face it hits, and then pulls the player to the place where it attaches. The player will stay secured there even if he switches to other items, such as tools.
The hook disengages if the player "fires" it again, if the player takes damage, if the block to which the hook is secured is destroyed, or if the player crouches (this would be a nice way to detach without having to let go of whatever item you are using.) When disengaged, the player will fall straight down if there are no blocks supporting them (as opposed to being somehow propelled away from the block face.) The hook can be immediately refired if desired.
Should the hook hit a mob, it will pull it to the player, much like the fishing-pole, but with a great deal more force. (Don't accidentally hook creepers, kids)
Uses:
Primarily for working on tall constructs, such as hard to reach Solar Flowers, or in delicate redstone constructions where placing a block is either impossible or would affect the redstone current activity. Another obvious use is just getting around in caves and such.
Power:
The grappling hook uses an RE-battery as a power-source, and thus has the same power reserves as the chainsaw and drill. The hook consumes a small amount of power when fired, a larger amount when drawing the player in (dependent on distance to be traveled, and if feasible to program, weight of the player's inventory), and a small amount constantly as it holds the player in place. Detaching requires no power. Because of its small power requirements, the grappling hook can be run off a batpack.
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I know the jet-packs fulfill a similar function, but this grappling hook would provide a more precise option for construction concerns, and does not have the mobility to really edge out the jet-packs in the travel department.