- Mechanical Keyboards - If you do lot of typing or want the keyboard to last more than 6 months without WASD-sector losing its feel, worth it. Albeit I'm against paying extra for the bling leds and such.
- 120 Hz monitors - If you have the kind of hardware to reach the fps to take advantage of 120hz monitor, you probably have money to buy one. One of those thing that you don't really need but can't go back once you have had one.
- 60+ Euro/dollar mice - Only if you need insane amount of buttons not found in sub 60e mice, yet again I'm against for paying for bling or maker logo. I think the sweet spot is 40-60, that gets you a decent gaming mouse.
- 100+ dollar headsets - Only if you're audiophile.
- dedicated soundcards - Same as above, you will want to get both though.
- Eyeinfinity - Gimmick, not fit for serious gaming and not very suitable for many types of games. Also requires tremendous hardware to run games smoothly. Yet I highly recommend having a second monitor.
- Nvidia 3D vision - Same as eyeinfinity.