Throwing out some ideas for some special fusion-only metals, mostly just as alternate recipes.
Zinc (Zn, 30) + Aluminium (Al, 13) = Technetium (Tc, 43)
Technetium is used IRL to produce electrons without gamma rays so maybe you can place it in a reactor and while it slowly (half-life IRL of 4.2 million years) degenerates into Ruthenium (Ru, 44), it produces maybe 1 EU/t.
And then Ruthenium IRL is used to harden Platinum so maybe using it in some recipes would reduce costs?
Also Ruthenium (Ru, 43) + Beryllium (Be, 4) = Silver (Ag, 47)
Copper (Cu, 29) + Carbon (C, 6) = Bromine (Br, 35)
Bromine could be used to make Fire Retardant suits (Advanced Hazmat?) or used as additive to petrol.
Also Arsenic. Zinc (Zn, 30) + Lithium (Li, 3) = Arsenic (As, 33)
Maybe make Industrial Splash Potions of Wither?
Germanium. Zinc (Zn, 30) + Helium (He, 2) = Germanium (Ge, 32)
Germanium could be used as a replacement for Silicon in most recipes. Maybe even give more.
Cadmium. Silver (Ag, 47) + Hydrogen (H, 1) = Cadmium (Cd, 48)
Cadmium-Nickel batteries. Either as a replacement crafting recipe (give 16?) for RE-Batteries or a new battery that stores 150k EU.
Cadmium (Cd, 48) + Helium (He, 2) = Tin (Sn, 50)
Silver (Ag, 47) + Lithium (Li, 3) = Tin (Sn, 50)
No idea why people would burn tier-2/4 metals to get tin though.
Antimony (Cd, 48) + Lithium (Li, 3) = Antimony (Sb, 51)
Tin (Sn, 50) + Hydrogen (H, 1) = Antimony (Sb, 51)
Could be used to make advanced hazmat suit. Also smelt with lead to get Antimony-Lead alloy that could be used to replace Steel in some uses.
Cobalt (Co, 27)
Iron (Fe, 26) + Hydrogen (H, 1) = Cobalt (Co, 27)
Chrome (Cr, 23) + Beryllium (Be, 4) = Cobalt (Co, 27)
Titanium (Ti, 22) + Carbon (C, 6) = Cobalt (Co, 27)
Calcium (Ca, 20) + Nitrogen (N, 7) = Cobalt (Co, 27)
It could be used in electroplating (maybe stainless steel in GT in the future?). It could also replace lapis as blue dye in some recipes. Lithium cobalt oxide (LiCoO2) is also used in most Lithium-Batteries.
It's interesting how GregTech fusion just screws neutrons.