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I think a folder will be a better choice for an Altoids kit as it will allow you to include a knife with a longer blade.
There are some great options out there, my choice would probably be the Cold Steel Micro Recon 1.
Has slim, flat profile and a strong lock suitable for survival tasks.
I like keychain knives because you always have them when you need them. But I don't want a toy either. I currently have the Cold Steel Micro Recon 1 Spear Point Tactical Folder Knife. I feel like a fish out of water without it.
Cold Steel Micro Recon 1 Spear Point Tactical Folder Knife [link]
Cold Steel Micro Recon 1
I've had good luck out of my cold steel knives. I keep this one on my keychain.
Maybe the Cold Steel Micro might work for you.