None of the items you listed would be on my short list of indispensable kitchen items. The mandolin is the most practical of the three, and very useful if it suits your style of cooking. The smoking gun and grill will sit and collect dust.
The Kyocera slicer Margaret Pilgrim mentioned would be a nice stocking stuffer type gift. I’ve used one for years and find it does 90% of the things I would do on a mandolin. They are inexpensive, don’t take up much space and would let you get a sense if a real mandolin is something you would use often. If the slicer sees a lot of work, you could look to upgrade to a real mandolin later.
Items I personally find very useful:
1) If you don’t already have a high quality sauce pan and frying pan I would upgrade. Demeyere, which I like very much ,goes on sale around Christmas.
2) A high quality Dutch oven. Staub often puts a 3.5 quart oven on sale at this time of year.
3) Vitaprep/Vitamix
4) Microplane grater
5) Unicorn peppergrinder
6) Japanese knives if you don’t already have a high quality chef’s knife
7) Thermopen or thermopop.
After that I’d personally rather spend the money on ingredients I’d be excited about using than tools.
