I love explosives. End game, it's probably the most powerful combat skill. For SPECIAL, you should get some strength for some of the weapons. The best weapon, Mercy, has a strength of 8, so keep that in mind. You can go straight to 8, or go to 7 and buy implant, or 6 and get Weapon Handling, however you want to go about it.
Perception is nice, seeing as it affects explosives a bit, but it's up to you. It's always nice though.
Agility can come in handy with some of the weapons such as the Grenade Rifle and reloading the GmG/Mercy. As for Luck and Charisma, meh, who cares. Choose em if you wish. Oh, and Endurance is nice! Nothing svcks more than blowing your self up and can't recover from it. I'd say focus on STR,END, and AGI/PER. The others are up to you.
As for tag skills, you should tag Medicine or Survival, since you may blow yourself up once or twice. Also take something like Barter, since explosives aren't cheap. A 40mm grenade is 18 caps. At some point, possibly invest in Repair.
For weapons, use anything you can find really. Grenade Rifle, Grenade Launcher, whatever you can find! There isn't much variety. If you can, head to
for the Mercy, the best Explosives weapon in the game.
For Perks, take any and all explosives related perks such as Heave,Ho! which actually affects grenade rifles and such. Demolition Expert (3) is always nice for Overkill, and Splash Damage and Hit The Deck! all work together nicely.
If you play hardcoe Mode, take the Spray and Pray perk, or leave your companions at home. If you think you can do fine without hitting them, great.
As for just general tips, befriend the Boomers. They are reliable Explosives merchants. The Explosives build I used was more of a tank character, and by Hoover Dam had a certain family's Tesla Armor/Helmet.
Yes, it is possible to do the game on very hard only using explosives. I've never used Explosives as a support skill, I've always used it as a primary combat skill. However, I usually up Melee and grab a Super Sledge, which works great.
LONG LIVE EXPLOSIONS!