Computer

To get a future-proof computer, you need to make sure it has these features:

Nitrox-capable. Just like regulators, Nitrox compatibility costs peanuts and is a lot cheaper than having to buy a replacement later.

Gauge mode. For advanced technical dives, you need a computer that functions solely as a depth gauge and timer.

Not air integrated. AI costs a lot, contributes very little of value, and is useless if you have more than one cylinder to breathe from. If you decide you absolutely MUST have AI, then go ahead, just make sure that the computer you get doesn't make decisions about deco obligations based on your breathing rate, unless you really want a freeflow or OOA situation to triple your deco requirements.
(And no, that's no exaggeration - a fellow club member did a dive once, his buddy had 20mins deco on his computer, whereas his AI gave him 75 minutes, solely because he got a bit out of breath at one point on the dive)

I use: Uwatec Aladin Pro Ultra, Uwatec D-timer, Sensus Pro dive recorder, Decoweenie dive planner