There's a small gap between the side of the door, apparently you can place a landmine in between there.
Video shows how to place it and what map this works on

[Video: http://https://www.youtube.com/watch?v=fuojjW9sLgE]

Here are some additional spots I found, should work in TDM & FFA

[Video: http://https://www.youtube.com/watch?v=oNaD9OScIjY]
[Video: http://https://www.youtube.com/watch?v=6NZX_ROQ7jk]

Smoke Bomb only effects the screen making it difficult to see surrounding for everyone, however I have found two possible uses:

Gravitational Shot: If a player shoots a Gravitational Shot within the Smoke Bomb it will be complete hidden, however you can still hear it.

Optical Cloak: If a player enters the Smoke Bomb area while Optical Cloak is in effect, they will be complete invisible to all players. (But using medkits/anti-alinement/reviving other players will show a screen for a few sec