None! Self custody your bitcoin. Anything else is dangerous.  

 But I'm a NPC 

 Ok then, you're blocked!  

 Your Cold Card. 

 I only have credit card, does it work? 

 You can use it to buy a cold card.

https://store.coinkite.com/store 

 Why on earth do you want them to keep it? Just give it to me then 😁 

 I'm a NPC, and a nocoiner