It's better to find ALL 160 locations of Fallout 3. That way so you won't have that much walking to do.
Article #2: Secret Weapon Locatios:
#1 Lincoln's Repeater- Muesum of History- [link] After that.. there is more stuff in the SAME building of the rifle. You need to search EVERYWHERE in that building.. including book shelves. Such as Abe Lincoln's:
Civil War Draft Poster
Wanted Poster- guy who killed Abe Lincoln.
and a big Abe Memorial poster near the Voice.
DO NOT SELL THESE ITEMS.. IT'S POINTLESS.
#2 The Tenderizer- [link]
#3 The Xuanlong Chinese Rifle- [link]
#4 Fisto- [link]
#5 Vengeance (Powerful Gatling Lazor)- [link]
#6 Butch's Toothpick (switchblade)- Kill Butch at the Bar in Rivet City. Easy.
#7 Zhu-Rong v418 Chinese Pistol (shoots fireballs)- [link]
#8 Alien Blaster (one shot..enemy turns into ashes) [link]
#9 Experimental MIRV (Fat Man that shoots 8 mini nukes at the same time)
#10 Reservist's Rifle (Powerful Sniper rifle) [link]
There is more secret weapons I found.. but I can't focus right now.. NOTE me if you want MORE secret weapons!!
T-51b Power Armor location: [link]
Talking Medical Power Armor location: (watch out for A LOT of Deathclaws)- [link]
To get past the Enclave's force field shield without doing the main quest: First.. fast travel to Rivet City.. head towards the force field. Save the game.. because you might get stuck and can't move. There should be a pile of rocks on the right side of your view facing the shield.. jump on the rocks and walk left.. and you are on the other side.. now you can get Col. Autumn's multi-shot lazor pistol. Remember.. don't talk to him.. kill him on sight. His lazor pistol will not be in his inventory.. search the ground where he dropped it.
Thank you for you time gamers! Explore the Wasteland.
Enjoy the game.. and THANK YOU Bethdesa!!