Some of my favourite equipment items are:

• Backpack - this shouldn't need explanation and is a must have for the character that loves mundane equipment.
• potion of healing - of course, but can be expensive.
• Block and Tackle and Crowbar - a bit niche use, but can be amazing in dungeons for problem solving!
• Climber's Kit - again, may not see use, but if you do get into a situation where you need to navigate a dangerous climb, this will save lives (or spell slots).
• healer’s kit - another piece of equipment that stops people dying.
• thieves’ tools - someone in the party should have some, even if they are not proficient with them, you can still use them, just with your base dex bonus.
• Magnifying Glass - this often gets ignored, but the ability to get advantage on a check to inspect something detailed can be super handy.
• Antitoxin - can reduce the need for those potions of healing!
• Shovel - digging a hole without one is a miserable experience. Adventurers sometimes need to dig holes.
• Caltrops (bag of 20) & Ball Bearings (bag of 1,000) - a great way of restricting the battle situation in your favour if you have time to prepare in advance, or need to cover an emergency retreat.

The list grows massively if my characters get their hands on a bag of holding!