The internet (this has enhanced my life in numerous ways). Although the net is certainly no substitute for social interaction in person, it has done a lot to reduce feelings of lonliness as I can form relationships with people without having to spend loads of money or deal with the inconveniences and impracticalities of meeting up with people IRL. It also effectively grants me access to pretty much all of man's collective wisdom at the click of a mouse or tap of a button.
Probably an airplane. I'm looking to buy a single engine plane right now because they are pretty cheap. This one is under $30,000, seats 4, and uses only about 8 gallons of fuel per hour (it can use automotive grade). Max speed is ~120 knots (~140mph), with a range of around 500 miles...
id have to say the paper shredder. i fucking love paper shredders! i had a really good fellowes one but like an idiot i accidentally put a sticker in it, so ive been without one for a minute. i dont even want to try and fix it, i want a new one. my moms paper shredder is really good you can shred fucking credit cards you put things that are stapled i mean that god damn shredder is great. it shreds the paper into zig zagged pieces that look like confetti!!!! i get the free pennysaver and midweek just so i can shred it. my mother gets irritated with me because everytime i go out to her house, i use her paper shredder. i also like the sound of it its quiet, but at the same time loud but not noisy, if that makes any sense. paper shredders are fucking awesome!!
^ I love paper shredders too, but only because I am able to recycle the paper more usefully than most. I use it for my new worm farm and they love it. There you go, there's another invention, the wormery. It allows you to recycle kitchen scraps to produce vermicompost, something people will pay a lot of money for. No wonder they call it black gold.