These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Music: Not only are there several Ear Worms as noted below, but overall the music is very rocking and does its job of getting you pumped for the slaughter. Especially the boss battle theme, and its epic triumphant coda.
The remake will feature remixed versions of the original music, as evident by the TREMENDOUSLY AMAZING song in the trailer.
The multiplayer trailer introduces several more remixes. Notably, Run Like Smeg is now heavier-sounding, Havana Smooth gave birth to a dubstep hybrid and How'd I Do became even awesomer. Goin' Down the Fast Way and several other tracks are available for free listening on the dev's Soundcloud.
One of the lesser advertised features of the remake was a set of buttons on the main title screen in the bottom right corner, which allows you to cycle through all the music tracks in the game, with the 'Classic Mode' option for the music working here as well.
Demonic Spiders: In both the original and the remake, the Death Monks and Death Fire Monks. In the original, the former close in on you and try to suck the health out of you at point-blank while the latter shoot rather painful fireballs that move fast across an area. They both have a lot of health and are nearly the only enemies in the fourth episode. The remake worsens this by increasing their range (Death Monks can now damage you from several feet away, Death Fire Monks have homing fireballs that do burning damage if they hit you - kiss your ass goodbye if you've only got a little bit of HP left) and letting them glide towards you faster than any other enemy's normal speed. The only thing the remake's Death Monks have over the original game is a significantly reduced health, but you can be sure the final levels plop them down in unexpected locations all the time just to spite you. The only saving grace is the remake's terrible AI that requires you pop in and out and take on one at a time.
The Triad Enforcers are a close second to the monks, given that their M60s and grenades, along with their high health, will ensure that encounters with even a small group of them will cut you down very quickly.
The game's platforming happens to be a Demonic Spider in itself. Upon release, when the game used an outdated checkpoint system, the game often padded out non-combat sequences with lots of platforming over instakill traps - platforming that required very precise jumps, timing, and a ton of luck to get through. Often placed between fights.
Ear Worm: The game has several rather catchy pieces of music in it.
That One Boss: NME (Short for Nasty Metallic Enforcer). He's the nastiest boss in the original game, bar none, due to being very fast, barraging you with a spam of homing missiles and a persistently-homing disc projectile that can catch you off guard. He can kill you in two seconds flat if he catches you without an Asbestos Vest. This is not an exaggeration.
Less drastic is that originally, certain enemies were supposed to have alternate versions who would be randomly cycled in with the regular ones, many of which were Distaff Counterparts. The severe increase in RAM it would've required (by 1994 standards) meant that none of them were used, but a single frame from each one can be seen in the staff roll.
According to loading screens, three dev teams from other companies showed their own take on ROTT before Interceptor Entertainment was chosen.
Weapons had limited ammo per clip early in development of the remake, as seen in the multiplayer trailer - the optional reload animations are what's left of this feature.