stratagy
For weapons on defense mode, I went with:
1. USP
2: S&W .357
3. G36
4. M-61 Vulcan
5. Famas
6. HK 21
7. Desert Eagle and Overkill powerup.
8. Desert Eagle and Overkill powerup got me so much exp, I was able to buy the GAU-8 on my next turn.
9. Immediately following that, I bought 250 more HP for my base, 100 more HP for myself, and the laser cannon. With Overkill and the laser cannon, I got 81k exp that level.
10. I bought all the weapons just for kicks and used the rest of my exp to buy HP.
11. From that point onward, I only used the laser cannon and spent all my exp on more HP until I got tired and stopped playing.