Well, I have some vastly different opinions. A tower shield is usually a good thing to use unless you have excellent brands on a smaller shield. The amount it can boost your shields is quite high even without a lot of skill, while sacrificing evasion - which isn't as useful.
The primary exception besides a good brand on a smaller shield that I wouldn't use a tower on finding it is if it would stop me from casting something I need to cast. However, I generally find it true that it's almost always better to train melee/armour/shields before even attempting to cast any spells other than low-level utility stuff, and then a lot of games you simply never find the gear or even need spells once you've trained what you need.
As for ranged weapons, in my opinion the hand crossbow is the best of them.I rarely use two-handed ranged weapons unless it's "sniper", or before I have found a good shield, or it's very early in the game and I'm not even training them and just taking advantage of some nice drop for awhile to supplement my tactics. It's not true at all that a hand-crossbow isn't useful late game. In fact, I just finished a game where I killed off a huge majority of vault 5 with one. You don't *just* want to use it for everything, but swap between it and a melee weapon strategically. Level 9-12 skill maximum should be sufficient for most games to add quite a bit of overall effectiveness. Would I don a tower shield at lowish skill and use a hand-crossbow? Heck yeah I would.
Throwing is theoretically awesome, and I suppose it's pretty good, but personally I'd still rather train for a hand-crossbow. That's a long discussion why though, but I could at least point to a couple things like, thrown weapons can't have properties from an artefact launcher..
I'd also use a shield on a troll using unarmed damage. I don't have formulas at hand to back up why precisely, but I have enough games under my belt to tell you it's more reliable. The jist here is that defence > offense.
I use broad axes with trolls as well as unarmed. Sometimes I use a combination of both. Unarmed being how you survive early/mid game or on extra tough targets for one-on-one fights, and broad axes being more helpful later on when you're constantly getting surrounded and managing god-based life on kill tactics.
Well, that's enough for now
Good luck.