Playing marginal hands aggressively for fold equity.
Here's an interesting and underused tactic.
PokerStars No-Limit Hold'em, $4 BB (6 handed) FTR converter on zerodivide.cx
Hero ($442.60)
BB ($1183.05)
UTG ($274.30)
MP ($537.60)
CO ($496.50)
Button ($627)
Preflop: Hero is SB with A:diamond:, 3:diamond:.
4 folds, Hero completes, BB raises to $12, Hero calls $8.
Flop: ($24) A:heart:, 8:club:, J:club: (2 players)
Hero checks, BB bets $20, Hero calls $20.
Turn: ($64) 7:club: (2 players)
Hero bets $30, BB calls $30.
River: ($124) 5:club: (2 players)
Hero bets $80, BB folds.
Final Pot: $204