My first go to game is Classic Traveller. While CT was mainly inspired by pulp sf it also certainly has trappings of space opera and more modern hard sf writers like Niven and Pournelle. The equipment lists for Traveller are a good solid inventory but there were a couple of things that I feel should be included because they are cool or just a great way of saying 'far future' to people. Since we don't expect a reissue of CT anytime soon here's my .02 credits.
1) Energy blade- no not light sabers (tm). Energy blades appeared some time before Star Wars. They were a staple of Mobile Suit Gundam. I don't need to be able to stop bullets with my blade. In a pinch a humble heat axe will do. Fusion plants already contain plasma to initiate a fusion reaction, making it into a (relatively) cooler blade should be doable before tech level G.
2) A 9mm handgun- check my earlier posts for these. Sometimes you want to have a gun with a little more punch than a body pistol but more concealable than a a Magnum revolver or autopistol.
3) Food pills- great stuff for escape and survival kits provided they lick that problem with the blueberry pies for dessert. Tang would be neat also. Whatever happened to Tang?
4) Flight pack- Grav belts are the gold standard but you might not always have a TL 13 world handy. A rocket pack or even back pack helicopter would be fun. If Traveller tech has fifty kilo missiles accelerating at several gee for 10-30 minutes it can certainly lift me for a few minutes.
5) Neural whip- Traveller needs more non-lethal weapons. A neural whip harkens back to Isaac Asimov's Foundation stories. A stun beam that just nocks you out is not a deterrent to a psycho. Searing pain makes rushing you less attractive. Optionally the whip could be extendable at the push of a button. Note that a bullwhip in itself is a nasty weapon that can also trip, entangle and cut with its tip.
6) Hand cannon- for when subtlety is not an option and you only have one hand free. Surely some firearms beside a shotgun do more than 3d.
There are my quibbles. Certainly nothing there is too hard to stat. I'd like to hear what you'd like added to CT