[x] Shadow
[x] Explosives
I think that, if at all possible, I'd trade our lustrian eggs for a griffon egg, preferably a double-headed one (get a friend Amber to help pick, if it's "luck"), and get some Amber help in raising it.
While I love our horse, and its pseudo ward-save is very good, being actually mounted means +1 armor (+2 if we put barding on it), not being subject to Killing Blow, and actually riding an incredibly murderous beastie (as in, WS 5, S6, A4 as baseline). Oh, and it flies, I bet anyone would absolutely love a chance at riding a flying mount.
It's a nice incentive to figure out the Indefatigable enchant, too.
No, I'm not jealous of Esbern and Seija, why do you ask?
For a weapon, definitely get a dwarf one, because theirs are plain and simply the best. I know it's better to say something general instead of picking outright, but I'd dearly love Kragg's "hits at S10" rune, especially if we can pair it off with two Runes of Striking. Who needs fancy "automatically bypass armor and wound" runes, if you can just take a good ol' "hits like a fucking cannon" one?
Triple Rune of Cleaving is also good (Killing Blow, +1S, AP); Master Rune of Smiting (D6 wounds) and Cleaving x2 (+1S, AP) or Striking x2 (+1 WS, re-roll misses) or Fury and Cleaving (+1A, AP); Master Rune of Snorri (hit on 2+) and Cleaving x2 (+1S, AP) or Might x2 (Against T5+, double strenght, D3 wounds).